I currently have Jack the Ripper and Gilgamesh along with queen medb is their anyone I should be on the lookout for to help my squad. Also what is a good squad composition.

If you're planning to use the crit stars that Jack generates to take advantage of Gilgamesh's really good crit damage, you'll probably want to take Queen Medb out of your party since Riders tend to absorb a lot of critical stars, which could hamper the damage that Gil could do.

Alternatively, you can just level up Gilgamesh's third skill to make sure that he absorbs all the stars he needs regardless of who his teammates are, but you'll need it at a pretty high level (6 and above arguably).

As for squad composition, maybe the usual crit support guys would work for you, like Hans or Cursed Arm Hassan. Alternatively, you could probably just find a good Waver off your friend list as a support also.