Your return in investments are commensurate to your earnings,you can't expect to invest 100$ and earn more than someone who put in a 5000$

It's just basically easy to figure out,the major constraints in investing is limited capital,and so since the rich have enough capital to throw about,definitely they'll earn higher than those with far less capital

Smartness,patience and less greediness are vital tools in trading/investing
But the major determinant is investment capital,without it, the aforementioned tools are useless