When moneypot.com just started, I invested 0.01 when it had a small bankroll, and I gained a decent profit considering I only invested 0.01, hence investing small amounts in small bankroll sites does work, at least in my experience.
You gained a good profit because you had a decent % of the house since the bankroll of moneypot was very little back then.
Wether you invest or not you still cant make a profit in the long run. It is still a gambling even you invest and no one can win the long run in gambling.
Your investing on the house and the house won't lose in the long run unless someones cheating every roll.