With $ 500 you can buy altcoin. This is a very good money making area today. But you need the wisdom and the market analysis techniques of altcoin. You can learn about altcoin on the internet
The big question is: which one. I have tried some in the past and some of them turned into scams or were sold to another team that couldn't promote it well enough. There are many decent coins, like Ripple or Dash, but you never know what becomes of them in a year or 2. It's a gamble.
If I were to invest i'd choose the king - Bitcoin. It's much safer than trying altcoins and offers a comparable chance of profit.