Yo bird fucker can’t you read? Mark 7 and The Visualizer laid it out for you already.
Seriously, it's not because of gamefly or for selective service.
You can't get credit because you don't have any credit. Odds are gamefly didn't even report you to a credit bureau.
Get yourself a checking account and a debit card (even if you never use it). If you haven’t already.
Then sign up for a visa or MasterCard offer that you get in the mail. One with a high interest rate and a low credit limit is most likely what you’ll end up with. Use it as much or as little as you feel safe with, but pay you bills on time, or even better early. Every few months call the credit card company and tell them you want a lower interest rate and a higher credit limit. Most of the time on the phone they will tell you that you can’t have it, but a few weeks later you will get a letter saying your credit limit has increased. This looks good to other companies when applying for more credit.
This will establish your credit and Best Buy will give you a card. Currently because you have little to no credit history you are a higher risk for never paying it back or using them just to establish your credit.