Hello, with 500$ you can invest. I recommend that you select the prestigious exchange, as i have suggested: Binance, Gate, Huobi,... And with 500$ you need to study coin, you choose to avoid losses. And the value of the coin you choose is as low as possible. Because the lower it is, you' ll buy more coin, and when the price increases you' ll get more profit. This is my personal opinion. 
If i have that $500 I'll convert it into bitcoin , because as we can see, bitcoin price now is quite good ,it is going up now a little by little unlike from the other days ago. And if my investment got interest, I will buy some altcoin so that I have a bitcoin and altcoin investment that could be for long term. $500 is such a good staring amount to trade.