Reny, we don't have a super Wal-Mart here (just a regular one with not a lot of grocery items), so I can't really advise on that. But what I did was to sign up with the grocery game for the $1 four-week trial. During that time you can have access to all of the lists that are available in your area. I checked each store's list every week and used the suggested coupons (so much easier than trying to keep track of all of the coupons on your own!). By the end of the four week trial, I had a pretty good idea which stores it was worth continuing and having to pay for the lists, and I kept the subscription to only those stores, knowing that I would save much more than the lists would cost.
The other thing that I do is to keep a spreadsheet of my "usual" stores and "usual" purchases. I keep track of the normal prices for the items I use regularly and I keep track of the lowest sales prices for those items also. It's similar to what you are paying for with the grocery game list, which tracks sales trends. However, I have found that on some items, the list shows things as being good deals when I can really buy them for less someplace else (Wal-Mart, for example).
I have saved a lot of money though and been able to stock up on things when they are on sale. There are a couple of free ebooks on the coupon mom site, and lots of instructions about how to use "the list" at the grocery game site. Read them! It will probably change the way you think about grocery shopping! And, yes, it can become a rewarding hobby! I feel great when I'm able to come home with several bags full of great deals!