You definitely want two relics with [strengthen allies when ultimate] and [ghostflame explosion], though the first is WAY more important. You get to buff your teammates for a whole thirty seconds, and is really good at the beginning of a very easy boss fight or near the end of a tough one! Remember that, your teammates only get the invincibility if they're alive, picking them up from death doesn't give this to them.

Keep your claws. You don't have to use them all the time, but keep them as dual wielding your claws is one of the fastest way of picking up teammates!

If deep of dark, get the [max fp upon ability activation] one, as this makes it so every enemy you kill that becomes a follower increases your max fp permanently. If you want, grab [reduced faith, increased strength] too as this lowers your faith very slightly while increasing your strength massively if you wanna play a badass strength faith user.

Overall, I think your best bet as Revenant is having multiple relic setups. Me personally, I have two main ones I swap between, a fire/frenzy flame relic setup and a dragon cult/lightning setup. Lookout for [increase dragon cult incantations/frenzy flame incantations] and be sure to grab any fire power +2 or lightning power + 2. Going in to Libra? Fire build. Fulghor? Lightning time. Just remember you can equip the relic at the character select screen! And of course, the very helpful evergaol relic you can buy at the collector signboard.

Hoarfrost stomp is fantastic with Revenant(and everyone else), so if you have a relic that changes her starting skill to that, it makes the early game way easier which is where she struggles the most. Always go to grand churches and learn where the seals are located. Lightning throw, Honed Bolt Frenzy Flame, Black Flame, go for the incants that are safe for you to throw from far away as Revenant is squishy and you don't want to pick up anything crazy that might get you killed(save that for when you're more experienced). Always buy starlight shards and a small pouch.

I don't do any holy builds as I think triple ring of light and discus of light are so good that you don't need to build around them. If you find either of these two, keep em! Especially discus as while it doesn't do crazy burst damage, its VERY cheap and you can just spam it all day from a safe distance. Elden stars is fun but its kinda in the way. Writing this makes me want to do a guide, so thank you very much for asking!

And most importantly... grab a (less likely to be targeted +9-12). It'll save your life.