The profits dont change based on how much you put in. You will get the same share in % just over more bitcoin so you must decide if $10 is going to make you enough to reach whatever your goal is and of not then increase it till it is.
Maybe you play world of Warcraft and want the subscription paid for. You need $15 a month so the investments gives 5% a month so you need 20x $15 because 100% / 5% = 20
So to get $15 a month you will need $300.
Remember investments are not fixed returns and can differ but I'm talking about the average. Anyone offering you fixed return is scamming you.
Invest in yolodice and see fpr yourself. Look at their profits. 100% transparent !