With horse racing I like to see a full year's results covering all seasons. Even then, you have to be constantly on the alert for changes beyond your control which may affect your selection method.
What I'd like to say is that since you are starting with a small amount enjoy it and let the profits accumulate. If you want to you can take a dividend when you double your bank and adjust the bank and bet accordingly. It is a great feeling when you are playing with other people's money.
I hope that is some help.