I placed some instructions in the instructions tab, however I think you are talking about within the game. I can see to that, thanks for the feedback.
*EDIT*
I have added a simple instructions screen.
Upgrades are nice, but what does "adds chance" mean? How much? Maybe have add percentage or numerical value to upgrades. Having different levels is nice too. How about labeling each level so we don't have to guess which one is next and hold the mouse over it to check. also maybe add and upgrade to slow the tumbler speed to make it easier to get a triple.
laggy? ...how strange. but if you want a more challenging play them in hard mode in fog of war mode