CGR
Priority is first 3 alone... But who's worthy???
First three don't gain a significant amount from the gem. CGR gets a slight boost to damage but through extra dps, not his attack rating or buffs. Galan gets slightly faster ramp up with the dupe and I'd say it is insignificant in most matchups, but stun immune during harvest is nice (saved me in act content). Hulkling's is the worst, gets slight buff duration increase (bulwark and fury) and higher pierce damage, but it only becomes significant at high sig. Angela and Hyperion have good dupe abilities (Angela needs high sig tho to stop damaging debuffs from occurring and nullify/autoblock while hyperion gets barely anything from stones (+60 percent duration of buffs)). Probably better off investing in these guys because they become really op (more OPer to say)
Hyperion, definitely. CGR's dupe is very unnecessary and offers almost nothing. Hyperion's dupe is amazing and needs only sig 1.