The main challenge that I see with a Small capital investors are to maintain their capital because investing it is really hard to choose wether it will grow or not in the currency they invested. And I think most of the time they always lose some of their investments because of lack of chance in choosing the good currency to invest.
You are right, small capital are hard to get more profit and chances are very small compared to those who have big capitals. And It is really hard to avoid loss in investments too.