InstaGC is a great GTP site. What makes InstaGC unique are two big advantages.
Payout options: Amazon, BestBuy, iTunes, Starbucks, Target, TotallyTickets and Walmart. Paypal has been removed :(
1) $1 minimum payout. You don't have to get points or other crap like that just earn $1 and cash out.
2) Instant gift card codes. Whether it's Amazon or Walmart anything else on the site, as soon as you redeem your points you get the code. Most other GTP sites make you wait a few days to a few weeks to get what you earned. If you have any questions about the site, feel free to ask. Good luck and also post your referral links in the comments if you want.
Referral Link:  earn gift cards

 As for tips, I use an extension called LastPass (click to go to their site). I use it for Chrome but the universal installer installs it to any browser. That lets you fill out forms with one click once you set up your info. Set up a spam email account too for doing offers. Use that email as your auto-fill email. Some offers make you confirm your email address, so make sure to check once in a while if you see that in the offer description. Also, they say if you clear your cookies/cache after doing offers you'll have a better chance of it approving. I don't do it after every offer, but if there are two offers that have the same layout then they probably share cookies/cache so I clear it. To find good offers, sort the offers by rating. Highest rating offers have the best chance of being approved. The ArcaMax offers are pretty easy, you just enter your email and click confirm. And finally, look at what offers are being approved for other members in the instaChat box. If they approve for them, it's probably legit and will approve for you too. earn gift cards