just buy the first to begin you will see how much you generate in a hour in that mentioned. You can increase the income buy buying more.

In christmass it was when you have 10 25 100 200 etc it did double the income it also did double when you has 1 o10 25 100 etc of everything.

The hardcore is a multiplyer reset that has ad disadvantage it will reset the game but you will in the end gain faster more star thingys The nipple server is a other multiplier but kinda expensive.

Then the upgrades unlocks you can also buy to make the income come faster also again on thoose stars

So in short you cann't do much wrong just not go the fastest. But in due time you solve that