I would say don't trade or invest in anything until you have a plan. $500 into a $50/$100 stock isn't going to go far and could take years to make money from. Are you willing to just sit there and add to it over time to build a long-term account such as an IRA? Or do you want to trade small caps with potential to make 10/20% relatively quickly? So first decide what you goal is right now. Do you want to learn to actively trade or build an account of quality companies over time? Then learn a strategy based on what you want to do. You're young, you could afford to be a bit riskier, but at the same time it's never too early to start saving for retirement considering you will need multiple millions to retire well.

Couple questions, I know your only 19, but do you have any credit card debt or a car payment? Will you have student loan debt when you are finished with college? Debt is slavery these days. You will be able to save much quicker thus having more for trading/investing if you are out of debt. Just keep in mind for future if you are free and clear right now. I mean, I know nothing about you, so who knows, that $500 may be best sitting in a savings account until you can save up more as an emergency fund or to pay off future purchases. You should keep all your options open for now. Take some time to figure out what is best for YOU.