Level 3:

Aura of Vitality For 10 rounds, you can use a bonus action to heal yourself or a creature within 30 feet of you for 2d6 hit points. Not bad.
Blinding Smite Compared to a Divine Smite, you trade 1d8 damage for the target being blinded until they make their save. Pretty good, shame it breaks your concentration.
Create Food and Water Hopefully by level 9 you'll have enough food and water.
Crusader's Mantle For this to deal as much damage as a level 3 Divine Smite, you'll need to get a total of 8 hits. Now that every weapon-wielding class has access to extra attack, that's not a huge ask if you have the right party composition, but this does require your concentration and makes the party more vulnerable to AOE effects.
Daylight Bring a torch.
Dispel Magic Thankfully the check is using your spellcasting ability, so you'll be just as good at this as a Wizard is. The effectiveness of this spell depends greatly on how many magical effects your party sees.
Elemental Weapon Neglecting the +1 to hit, you'd need to get 8 hits with your weapon for this to be as good as a Divine Smite, plus it requires concentration. If you don't already have access to a +1 Weapon, this gets a lot better.
Magic Circle The fact that this takes one minute to cast relegates it to out of combat use only, unless your party has a chance to set up an ambush in advance. While you get a fairly wide selection of creature types to choose from, it only works against one type, and humanoid isn't one of the options.
Remove Curse Very nice to have when a party member gets cursed, but I wouldn't keep this prepared unless I knew I needed it.
Revivify This one, I would keep prepared at all times. One minute is usually enough to finish the combat but not enough for you to take a long rest and prepare it. Obviously far less good if your DM won't kill you.

Oath of Devotion
Beacon of Hope Great just for the advantage on wisdom Saves, though maximized healing could come in handy too.
Dispel Magic is already on your list

Oath of the Ancients
Plant Growth You could use this spell to significantly slow the enemy down while your ranged allies take them out, but beware that it affects you too. The second application is very campaign-specific.
Protection from Energy It only affects one creature and only grants resistance to one damage type, but you'll be glad you have it when you have to go up against a mad pyromancer or something.

Oath of Vengeance
Haste In order to make use of this spell, you NEED Constitution save proficiency so you don't get your concentration broken, and hopefully to be able to cast this before combat starts. Assuming you're using a greatsword, you'll need to get 2 hits from this in order for it to pay off (2d6+3 * 2 = 20, 4d8 = 18), though it also allows you to spend your other divine smites faster.
Protection from Energy see above

Oath of Conquest
Bestow Curse Some great effects here, notably the "wisdom save every round or you do nothing" curse. Once you get to level 17 and can make this last 8 hours without requiring concentration, it gets even better.
Fear Amazing for you because of Aura of Conquest. They can't move to a place where they can't see you, so they're stuck in place, taking auto damage.

Oath of Redemption
Counterspell Depending on how often you end up going against caster enemies, this could be very useful.
Hypnotic Pattern Finally, the Oath of Redemption gets an effective spell to break up a fight without hurting anyone. Single saving throw for 10 rounds of AOE incapacitation is excellent.

Oath of the Crown
Aura of Vitality is already on your list
Spirit guardians is amazing. It's friendly, it lasts 10 minutes, it slows enemies, it follows you as you move, and it does great AOE damage, which is something Paladins are otherwise lacking.

Oathbreaker
Animate Dead Get a permanent zombie friend, who's damage is boosted by Aura of Hate. Unfortunately, at 9th level, their low accuracy means they won't be hitting very often.
Bestow Curse A strong debuff that greatly improves at spell level 5 when it no longer requires concentration.

Level 4:

Aura of Life Necrotic Resistance and Immunity to max hit point reduction are good for Undead Encounters, regaining one HP at the start of each of your turn at 0 effectively means you can never die... until your DM catches on and starts attacking your party members while they're down. Remember that once you drop to 0 HP and fall unconscious, you immediately lose concentration, so the last ability will never affect you.
Aura of Purity Lasts 10 minutes, makes your party immune to disease, resistant to poison, and resistance to a plethora of debilitating status effects. Very good.
Banishment For one save, take any creature out of the fight for 10 rounds. Hooray.
Death Ward It only affects one creature and it only works once, so you probably have better ways to prevent an ally from falling due to combat damage. The usefulness of this will be depends entirely on the second clause. If your DM likes to hit you with Power Word: Kill, then this is one of the only effects that can save you from that.
Find Greater Steed What? Warhorse is evolving! *da du da du* Congratulations! Your Warhorse Evolved into a Griffon!
Locate Creature Hopefully, you'll know if you need a spell like this before you start your day. I wouldn't keep this prepared all the time.
Staggering Smite You lose 8 damage compared to a level 4 Smite, in exchange, the target must make a saving throw or have disadvantage... for one round. Yeah, no thanks.

Devotion Oath Spells
Freedom of Movement This will be a minor benefit 95% of the time, and save your life the other 5%. Seeing as you get it for free, that's pretty good.
Guardian of Faith 60 damage is pretty good value for a level 4 spell (A level 4 smite deals 22.5), and the effect lasts 8 hours with no concentration. However, since the guardian can't move, you'll have to position it carefully.

Ancients Oath Spells
Ice Storm The damage on this is 2 more than Fireball, which a Wizard got a whole 8 levels ago. That said, bad AOE still beats no AOE.
Stoneskin Lasts an hour, and gives a target resistance to weapon damage (even works against magical weapons) It's very good, just mind the expensive material component.

Vengeance Oath Spells
Banishment Is already on your list.
Dimension Door While the range on this is better than Misty Step, and it can go through walls, Misty step is at level 2 and this is level 4. The times you need this, you'll be happy to have it, but you probably won't be using it too often.

Conquest Oath Spells
Dominate Beast At this high level, you probably won't be running into many beasts worth dominating
Stoneskin Resistance to weapon damage is good.

Redemption Oath Spells
Olituke's Resilient Sphere You can protect yourself from attacks while you preach the virtues of peace, or you can use it as another Banishment, that targets Dex instead of Wis.
Stoneskin Resistance to weapon damage is still good.

Crown Oath Spells
Banishment is already on your list.
Guardian of Faith Same as for Devotion, a strong spell.

Oathbreaker Spells
Blight At this level, you have Extra Attack and Aura of Hate, your regular attack plus a level 4 smite will do much more damage than this. It's better against plant creatures, so it might be worth using against one of those.
Confusion It's AOE control, but it breaks on a save and has a 20% chance to do nothing. The area is also really small.

Level 5 Remember that the cap for Divine Smite damage is 5d8, so a level 5 Smite doesn't do more damage than a level 4 Smite.
Banishing Smite This is the only Smite spell which actually does more damage than a Divine Smite of the same level, and the banishment effect is just gravy. The one mark against it is that it breaks your concentration.
Circle of Power Now everyone can pretend to be an Oath of the Ancients! It's redundant if you already are one, but otherwise very much worth taking. At this level, spells and magical effects are much more common.
Destructive Wave While the damage is the same as for a 5th-level Fireball, it's friendly, it has a better damage type, and it has a nice upside of knocking Prone. Also, it's the only AOE spell most Paladins get.
Dispel Evil and Good Most of the effects of this spell are already given to you by Protection from Evil and Good, which is a level 1 spell. The one addition is Dismissal, which ends the spell, and requires both and attack roll and a failed save by the target to work. It's really bad.
Geas This isn't that useful in combat, since 5d10 damage to a single target once per day is unimpressive at this level, but it's extremely good for controlling NPCs. A king might rule over many lands, but he'll still probably be killed by 5d10 psychic damage. So this spell is campaign-specific.
Holy Weapon Bonus action cast, lasts an hour, and adds 2d8 damage to your weapon. You'll have to hit 3 times to be ahead of Smite damage on this, which is totally reasonable, plus if you don't need the buff you can trade it in for a small AOE that blinds. Very strong.
Raise Dead The material component costs more than Revivify, but the length of the spell is 10 days rather than a minute. I wouldn't prepare this all the time, but it's a lifesaver when you need it.

Devotion Oath spells
Commune Free answers to your questions. The usefulness of this is mostly up to the DM
Flame Strike Compared to Destructive Wave, this offers less damage, less area, and no control.

Ancients Oath Spells
Commune with Nature Scouting spell. Use when you need to scout.
Tree Stride This is basically free teleportation, as long as you're in a forest.

Vengeance Oath Spells
Hold Monster It's Hold Person, but it affects any creature. If you liked Hold Person, you'll like this too.
Scrying Lets you look at someone far away. If that seems like something you'd be interested in, great.

Conquest Oath Spells
Cloudkill You'd need to hit each enemy twice with this for it to be as much damage as Destructive Wave, plus it requires Concentration. The potential for it to do very high damage is there, if the enemies stay in the cloud for three or four rounds, but it's unreliable.
Dominate Person Offering the target a saving throw every round to escape is not the greatest, but the effect is very strong.

Redemption Oath Spells
Hold Monster see above
Wall of Force An excellent control spell that offers no saving throw and can split the enemy forces in half.

Crown Oath Spells
Circle of Power and Geas are both already on your list.

Oathbreaker Spells
Contagion This is far too slow to use in combat, requiring three failed saves to take effect. At this level, the kind of creature you'd want to apply this to, then wait another day or two to engage can probably remove a disease somehow. If you do manage to get this effect off, though, it's extremely deadly, especially slimy doom, which causes the target to be stunned whenever it takes damage.
Dominate Person It's a great effect, but it only affects humanoids and it gives a save every round.

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