So, you're selling codes to a fishy site using an autobuy platform while all your reviews are given by newbie accounts with 0 trust and allmost 0 history.

What could possibly go wrong  
In case somebody is missing the obvious sarcasm: you could get scammed at the autobuy platform, OR the OP could go for a double whammy and let you pay to receive an invite to a site that was setup to scam people...

There is no way a malicious user is going to sell you "dirty" BTC for 30-50% off, he'll just run it trough a couple mixers/coinjoins/exchange for XMR/hotwallets him/herself and only lose 5-10% instead.

For everybody reading this topic: if something looks to good to be true, it usually is... Don't get scammed...