Hey Gabriel. Glad to see the designer here!
The way I see it, the value of an early turn is about 12 gems. (some hubs give you 11 if you were to pass first action, and that would not be a very good move, even if it were legal.)
In a 2p game, the starting gems is 0/1, which makes the implicit value of a turn only 2 gems, as p1 starts half a turn ahead. If you believe the value of a turn is 12 gems, then an appropriate balancing is 0/6 in 2p, 0/4/8 in 3p, and 0/3/6/9 in 4p.
Of course, 12 gems might be an inaccurate value, in which case the balance should be different. In any case, I believe 0/1/2/3 is clearly too little.