The current meta is the Darth Revan+ Darth Malak and the sith empire.
To do this you also should have almost all the OR characters at g11/g12 (+ zeta on some).
Jedi knight Revan (with bastila, jolee, gmy and hermityoda/general kenobi/ezra/other good jedi) is close to the meta.
Another great option is the GG's droid team or the Padme's (+Anakin, Kenobi, snips) Galactic Republic team.
The geo Brood Alpha's team or the 501 Shaak's clones team also viable.
Note that there are ledgendary characters like R2D2, C3PO, Thrawn etc that can be very effective in more than 1 team (but some of those characters require an investment in other toons)
5000 crystals is not small amount, but not too high either. I suggest to focuse on 1 squad at first.
Pay attention to the mods and the gear. This could be no less of a farm than the toons farm.
Make a smart use of each farm source (regular/hard battls, cantina, fleets...)
Good luck