Their are free tourneys as well but they dont pay out. Master tier 9 hole single play winner receives like 162 credits. Think about buying some credits to start off, $1 equals 100 credits.
There are also offers from vendors, and you can also get your friends to join, typically if they buy credits you get a bonus (as well as a free sleeve of balls for them just joining).
Like tiffer said you need skills to get top 10 in ready go's. Match play challenges are also a great way, and you can choose to accept a challenge from another player. You can also sort the search results based on competitor level.
Also, you can see any players stats and scores by clicking their name. Its a good way to determine to accept a match, or determine how much you want to wager.