Hi! I've tried different races on different realms and to be honest Rakan is my favorite at this point. There are different ways to play them, this is my take on it:
- Silver turtles: one in the middle in small formations, one on each side in large formations. Almost always use the ale on them first.
- Silver crossbowmen: fill your back row, they can be passively boosted by both Mako and Yip, they're usually the ones I spend ale on when I need to finish a battle quickly, their deadly piercing arrows are quite the finisher
- Gold & silver samurai: great frontliners against small units, using ale on them helps saving a few but isn't vital
- Gold & silver monks: same as samurai, but used against large units; can also be passively boosted by Denji
- Silver ninjas: only have a few for when I need to go all out and have a few small holes in my formation, put Gold ninjas on wall when needingto decrease resources to deter pillagers
- Silver catapults: only when going against walls or lich armies, otherwise they gather dust
- Warship: honestly if you can get there, it's a devastating addition to your formation
IMO crossbowmen are the units to boost the most in research, they're solid enough as silver (and cost less ale to activate), whereas a strong and resilient front line is needed to protect them (hence the gold placement). If you can get all three Rakan heroes, they really do help; also Avalon as usual for the speed boost and Virion for the morale shield boost are stellar in Rakan formations. Vega can also be useful by helping protecting your troops, especially in void levels needing no casualties as Rakan are fierce but not necessarily tanky. For the rest, I'm fairly sure you can use whichever heroes you prefer to fill the field.
I hope you have fun with those adorable little beasts =D