Most people don't know about this feature, but it is really easy. You can take surveys, download stuff, and watch videos to earn AG. I think Payment Wall is probably the easiest since it has a lot of surveys for you to do.
If you don't have enough time to earn AG, you can just buy AG. $1.00= 100 AG. If you buy a large amount you get AG bonus. Also, buy AG when there are special offers like the other day you could get a Panda hat or a handhold doll. :)