You can use localmonero.co
(this is my ref link, if you feel helping me out :D ) localmonero ref link
You can buy directly with fiat and lots of other options there, without all the fees and verification from exchanges/etc. Feel free to pm if you have any question.
You can sign up to localmonero.co and post an add to buy monero there. You'll be buying monero in exchange for a game code. This service holds the xmr in escrow for you until you send the game code over the built-in message service.
You will just need to be sure that you can prove that the game code was valid at the time that you sent it, in case of a dispute. Not sure how you'd do that, but have a think.
Here are some guides for you:
https://localmonero.co/start/trade
https://localmonero.co/start/sell
The best method for selling if you don't want to get scammed is any irreversible method. So PayPal is reversible, meaning that it can be refunded back to the buyer after the trade is completed.
Cheap with KYC and credit card? kraken.com
without kyc, but at a premium and might take some time: localmonero.co
there are also BTC->XMR exchanges