Before decide to that matter,,you can do some research about the market move,,because its very important,,although in the past days, gem is surprisely boom in the market,,
- In optional suggestion to you my friend to go Binance exchange because its also great to your gem,,because its gives insight to which coin may  have the best bet in short term and long term, its also simple to used it for buying them..and that's why some people choose binance,, and lastly do not put your egg in one basket,instead put it into different crytpto currencies for minimized your lose.