Your 500 dollar investment in Bitcoin or ETH will be a better choice, especially in the current market, which is a safer way.
A safer ride is investing in the above 2 coins as mostly once the btc starts the bull run you will make money in both the coins. But if you are ready to take some risk and not really in need of this money then can invest in some of the other altcoins where you can make multiple times returns on the btc rise.