I’ll just say that for late game, try to get the 4 caster supports. They’re a vital part of team comps in general. While Hans is comparable, he just isn’t enough. You can still save for Waver, Tamamo and Skadi as they have upcomming banners next year.
As for the F2p servants, I’ll say prioritize the following:
Lu Bu-mindless red button. All around damage dealer to anything. Your best friend to f2p boss slaying even comparable and even surpassing some golds in damage.
Cu Chulainn (Orig)-your contingency plan. Can save you if your party is wiped out. Everyone’s favorite cockroach.
Robin-safer Lu Bu. Basically a nuke with attack down and self evade as bonus.
Euryale-male killer. The go to nuke when the enemy tries to assert its male dominance. Can charm stun too.
David-team evade with attack buff, enough said.
Hans-Bronze SSR support. Heal, attack, defense, crit damage and stars. Will also give NP charge later on.
Arash-absolute suicide nuke. Cleans the field of trash and allows 3 turn comps with his death.
Spartacus-he is all muscle. Zerk AoE w/ def ignore. Can be harder to kill than you might expect.
Georgios-meat shield. Use him when you don’t want other servants to die.
Mash-harder meat shield. Shorter taunt in exchange for team def buff and invincibility. Another SSR like support.
Mecha Eli-for mindless cavalry slaying. Very effective on three classes with decent damage output
Other notable ones:
Leonidas-red meat shield. Similar to Georgios but with Buster support
Shakespeare-Buster support w/NP charge
Amadeus-Arts support. Insta crit.
Ushiwakamaru-good nuke with attack buff and NP gain buff.
Caesar-attack, np, and crit damage support.
Inshun-Cu tier soloist. Has many many self buffs. One of the best for facecarding.
For, the rest of the f2p just pick 1 ST and 1 AoE for each class as a start. For golds, raise them all if you can. Also, please don’t burn until you NP 5 any f2p. Just don’t. You’ll raise them all in the end when you have nothing to do anyway.
Edit: Just to let you know, prepare your archers, zerks and sabers, especially some of the ones I mentioned. You’re about to taste true fgo hax after the next singularity from London.