well i guess the bonus doesn't even matter if i bought less than 1 ETH right??
so if i invest at stage 3 or 4 i will get the same amount of bitto right?
dont have that much money yet

Well it doesn't matter, but if you intend to buy 0.5 + 0.5, make sure it's in the same stage so you get the bonus.
0.5 in Stage 3 + 0.5 in Stage 4 don't give you bonus, but if you do both in Stage 4, you will get a bonus