You can purchase BitGems if you are unable to mine them using a pool. You are free to trade them on numerous exchanges using BTC Bitcoin. The advised exchange is Cryptopia as they are the most popular, reliable with the best volume and amount of BTG to purchase. BitGem is a very low coincap cryptocurrency currently in terms of very low amount of coins mined and minted, around 50k presently so they are VERY rare unlike many crypto’s with billions or many millions.
You can send BTG to your own wallet or store them on the exchange after purchasing. Storing on your own wallet is highly recommended for security along with the fact that when the coins are mature you can stake them and receive additional coins via minting for virtually free.