Misty Step and and find Greater Steed. You seem set with plenty of utility control spells already and you have other utility from wizard and cleric part members. So these spells will be to give some mobility options for you, making the battlefield safer to manuever.

Misty Step is a great bonus action teleport for low spell slot cost to help escape dangerous situations.

Find greater Steed is just so much fun to have, the mobility is great and having an intelligent pet that you can telepathically communicate with allows for fun roleplaying. Going into a dungeon I would rate lower but still just too much fun not to take it. The steed lasts until killed so precast before the day begins. Due to cramped spaces of dungeon stick to the Large sized choices of Steed and remember that you don't have to mount them, IMO treat it as a utility pet to bring up the rear. When the space opens up it will be very useful to have a non concentration flight option handy, you can lend it to your paladin they will appreciate the support.

Oh and I think misty Step affects your mount too when you cast it.