rjmatalon, there are many ways to obtain credits here at WGT.
Check out the Tournaments, many of the weekly tournaments can be entered in for free and pay off with credit prizes. Some tournaments can also be entered for "X" amount of credits, and will often pay off with larger credit prizes or real life prizes.
Another way to earn credits is by playing in Ready-Gos. Ready-Gos cost 100 credits ($1.00) to enter and pay off a top prize of 550 credits ($5.50).
You can also complete offers for credits. By completing offers, the companies will then notify WGT and the credits will be deposited to your account within 48 hours. Some offers may require you to sign up and pay money to complete, but they will pay off with a lot of credits. So in essence, if I wanted to sign up for one of the listed offers, I can sign up and get WGT credits, killing two birds with one stone.There are also free offers, which don't pay out as well and are often surveys. Check out the Offers Page to see a complete list of available offers.
The final way is by playing in Match Play Challenges. You can wager a minimum of 100 credits and a maximum of 2,000 credits in a regular Match Play Match. I think whoever wins gets 90% of the total credits wagered... I can't remember correctly.
To play in Ready-Gos or Match Play Challenges you must be in a qualifying state.