So we'll divide up the island into territories of sorts depending on how many people want to play in the first round. If you don't know how mancala works (or this variation for this game, seeing as there are all kinds of evolutions of the ruleset), in this game you pick up a pile of gems from within your territory, except you are not restricted to a single direction of travel like in normal mancala (usually counterclockwise if looking at it from above), you may pick any of the four orthogonal directions (we could even go for the four diagonal directions too, I mean this is pretty flexible, I don't know how it will work out haha) and go in that direction until you run out of gems. If you place the last gem in an empty space, you stop there. But if you place the last gem in a populated space (with more gems), you pick all those up and keep going (in the same direction? or would we allow to fork into a different direction at that point? these details can be ironed down after playtesting I'm sure), and you can just keep going and going as long as you can. Whenever you go past your own chest, you drop a gem in as if it was a space, but you skip over everyone else's chests. If you drop the very last gem of your turn into your chest, you get to go again.
Originally mancala is populated with 3 gems in every spot although that may be too numerous here. It could be a checkerboarded pattern (so split into two mutually separate sets connected only by diagonals), with one diagonal set being empty spots and the other diagonal set having some gems in them.
The other thing still up in the air would be the placement of the chests. I was thinking actually if it was 9-by-9 and we had something like this, where O is a normal space and X is a chest:
OOOOOOOOO OOOOOOOOO OOOOOOOOO OOOXXXOOO OOOXOXOOO OOOXXXOOO OOOOOOOOO OOOOOOOOO OOOOOOOOO
And then you wrap around, so when you get to the top, you go back to the same column but at the bottom, etc. Also I'd imagine that gem pile in the middle would start off with a ton of gems or something, but it wouldn't be part of anyone's territory and thus could only be picked up as a result of being dropped onto.
Well whaddyall think? As you can see it's not a set-in-stone plan or something but I think it could be interesting