If you already have all the GW, arena and cantina chars you want you can spend them on:
GW --> all 3 ships --> shard shop currency --> gear
Arena --> credits / prestige mats
Cantina --> ship credits
The devs have said that there will be no new chars for those stores.
Jyn - can be farmed in the guild store (easy) and guild event store (but: HY > Wampa > rest)
Cody - can be farmed in the guild store (easy) and fleet store (easy)
Maul - can be farmed in the guild store (easy) and fleet store (easy)
Zam - can be farmed in the guild store (easy) and fleet store (easy)
Fulcrum - can be farmed in the fleet store (easy)
Echo - can be farmed in the guild store (easy) and fleet store (easy)
Chirrut - can be farmed in the fleet store (easy) and guild event store (but: HY > Wampa > rest)
All of these characters are easy to farm, you just have to set a priority order as you obviously cannot farm them all at the same time.
And some chars are just hard node farms (mostly the useful chars), because CG wants you to spend crystals for energy and node refreshs.
