The only dedicated support I’m seeing here is CasGil, and he naturally pairs well with Arts DPS, like Nero Bride (who actually is a support in her own right as well, but a little less so until she gets that coveted NP charge upgrade).
Borrow a friend’s Waver to pair with your favorite AoE or ST DPS Servants since he’s card-agnostic. Borrow Merlin if more Buster damage and/or his invincibility or other crazy features are desired.
Ilya is more of a specialized use for big boss (read: mainly Assassin or Berserker) killing and isn’t terribly great for general farming, being a ST Servant with low face card damage. First Hassan makes great memes, but likewise is not a daily plug-and-play.
Archer Gil is all around fantastic for many reasons, so borrowing a useful support for him is a winning strategy for many fights and for general farming.
For “F2P,” Hans is a safe, stand-out choice for ascending since his investment requirements and party cost are extremely low for the utility he brings to any party. Arash, as always, deserves mention for being an incredibly cheap and useful QoL bonus for any Master.
Berserker of El Dorado is a really fantastic ST DPS, while Fran is AoE and more situational. Her damage is quite good, but you need a plan to deal with her annoying self-stun unless you’re only going to use her to clear a 3rd wave.
P.S. You can mostly ignore Emiya Assassin in favor of the welfare Shiki, who is coming again relatively soon. Rider Ishtar is quite good IMO, and will only get better come summer when Skadi arrives. Marie is a low-priority pick since the only thing she’s really great at is not dying. Lancer Raikou is extremely powerful…Assassin of the Nightless City is solid for her role, but not an urgent pick. Emiya Archer is mostly redundant since you have Gil, but can use him for Arts AoE with CasGil if desired. Orion I have but barely ever touch, so I can’t speak well to them.