Thanks for the heads-up on the free game, Power of Coin. I've been playing it for the past three days. Pretty addicting. It was annoying, early on, having to wait for my coins to replenish, but as I unlocked prize sets I was able to go longer without running out of coins, until I reached a point where I'm now constantly gaining coins.
The best prize set is the sword set. Unfortunately(in my game, anyway), the purple sword is the rarest prize in the game. I was able to complete every other level 3 set, before I even completed my level 2 sword set. Fortunately, the level 1 sword set is the best one, letting you collect prizes even when they fall off the sides.
Also, in case anyone else was wondering what the jackpot does, I was actually able to achieve it, once. When you finally collect 3 orbs, nothing will happen, yet. Just keep playing until you reach Zeus, again. This time, Zeus will take an extra long time to defeat, compared to other times. I'm guessing this is like the game's final boss, even though it still loops infinitely after you defeat him. Anyway, after you defeat Zeus, while having 3 jackpot orbs, the jackpot fever will trigger, and 2000 coins will rain down for a period of time, granting you many coins and prizes. I was around level 200 when I finally got the jackpot, but I know I missed at least one orb, earlier in the game.
At this point, I see no reason to keep playing, since it's almost impossible for me to run out of coins, now, and there is no goal of prizes to keep striving for. I didn't spend a single cent on IAP, but if one were impatient and wanted to know what the best purchase is, it would definitely be the first level of the sword set. That 99 cent purchase will save you a lot time, waiting for coins to replenish.
As for strategy, try to keep the coins piled high so that you're more likely to get bunches of 4 or more coins to fall at a time. That's what triggers prizes and special coins to come floating across the screen.