It's a slow build up. Here are some basic Gift Hulk
1. You need to do the Treasure Box daily and use all your keys in hopes to win permanent keys. The more permanent keys you have the easier it will be to gain more coins. As far as I know there is no limit on how many keys you can have. I have 29 right now, so I get that many chances at free coins, etc.
2. Use the search plug in for a free coin daily and chances to win more permanent keys, coins, etc.
3. Every now and then I do a survey when they have an attainable goal like 'Earn 75 coins via offers and get a permanent key'. I'll watch as many videos as I can and do a survey to hit the goal. Surveys can be good for 60 coins or so.
4. Check the newsletter for a free Fountain of Youth code worth 5 coins. They send them out about once a week.
5. Also, like Cage said, when you get that bonus % for the offer wall, use it, if only to watch a few videos for easy coins. You can get an easy 10-20 daily alone from those videos.
That should help you get at least one gift card every 2-3 weeks at first and then they should come a little faster with luck and persistence.