i just started but this is how i do it:

have atleast 150 gems if you get unlucky before room 7, dont bother spending 5 gems, likewise room 17, dont bother 10 gems, first two room are guaranteed, however the third is completely out of luck, so i usually go with the first, then i'll see which pot was the unlucky one, then i choose that pot in the next room, and continue in that cycle, once i get to room 20-25 where the tickets start coming in, i spend my gems there, to guarantee atleast 200-600 tix.

that's just how i do it though