I really like these game, it is good for relaxing and just looking them fall through the path is satisfying. But the value design is just off balance.
Basically, anything other than the first few balls are purely garbage. Just look the screenshot below.
Both took about 740000~ cost, the first ball will increase your income by 1107 every 150 ticks, while the 6th ball, only increases 222 every 555 ticks. And this doesn't count the potential income for balls survive more than 1 zones. So I really think there should be some changes to the ball value and cost. As I believe most player will expect the later balls be more effecient than earlier balls. At least in the long run it should be more rewarding. Even upgrading the zones can increase your income more than that.
And about the tokens
Use them on Zone modifier, Ball modifier, and Token Gain.
Never waste your tokens on click income or click size. You are playing an idle game, and any ball survive 1 zone can give you much more reward than clicking it. (you have 30% chance to get 100% more income for the ball surviving the zone, so that gives you a expected bonus for 30%, comparing to the 25% bonus income for click reward)
Double value doesn't worth it at all. It only gives you about 1% increase (1% chance to get 100% extra income) while Zone or Ball modifier gives you 10 times more than that.
Zone unlock discount are useless, as later balls is very ineffective and earlier ball doesn't likey to make it for 3 or more level (30% * 30% *30% is less than 3%), so unlocking many zones are very poor choice.
Survive chance does help, but too expensive while the effect is small. Just use as a last option
My suggestion:
1. Either significantly increase the click reward, or change how click works (Like it works as making the ball touch the line at this zone)
2. Increase the effect on Survive chance, or lower the price for it. Like only leave it with 10 levels and each level increase 5% instead of 1%
3.Replace the zone unlock cost to ball spawn time or ball upgrade cost. That gives much more significant boost to the game. And fix the ball cost/income ratio for later balls.
4.Increase the chance for double income. 10% per level could be a good number as it gives about same bonus for other bonus upgrades.