In general, you want servants who would benefit you a lot from staying alive.
1-Asterios: He was already OP without grail ascencion on some stages, with 10k hp and an actual atk stat he can be used anywhere and shine.
2-Bedivere: Strongest single target NP after interlude, she breaks shit.
3-Hans: Dude was always good, but dies pretty fast. With a good hp stat he acts like a real gold servant.
4-Leonidas/St. George: This is a tie, pick the one in the class you are lacking most. Both are broken tanks only balanced by low stats. Leonidas supports Buster memes while George is more for stall teams.
5-Cu Chulainn: This is the one most people have Grail ascended and for good reason, he deserves that golden frame. He also is fucking strong.
6-Romulus: I've never seen someone grailing Romulus and I already have too many gold lancers. But check out his skills, at level 10 he heals 5000 hp every 5 turns, gives guts and boosts atk for everyone.
7-Any of the 3* Archers. Really, pick any of them. Euryale is better than Orion even without grails, Robin has been a meme for 2 years, Ko Gil is the closest thing to real Gilgamesh you'll ever have, Billy the Kid has the strongest crits in the game and David has Jeanne's NP as a skill.
8-TAIGA: She's worth it if you ever get her to NP 5, but she doesn't get any rate-ups. Her NP 5 hits harder than Scathach at NP 1 and her crits are ridiculous. Also has a badass black suit.
9-Spartacus: If you are a fan of him and know how to use him, well, he becomes many times better at being immortal. Won't do much damage, but he's at over 10k hp regenerating a lot of it every turn, only balanced by having the lowest atk stat.
10-Medea: She's probably the only Single target NP Caster you have, she can't be replaced on many teams so it's good to use her at full potential.
Now someone save this shit, it's the ultimate knowledge
