Antonio ... other than buying credits, there a weekly tournaments in which you can win credits by scoring in the Top 70. Not the fastest way to get credits, but it won't cost a single peso.
PS ---- This is a real pet peeve of mine. Everybody was new here once, and most of us asked the same simple questions. True, the search feature hasn't always been here, but in the time it takes you to point out the search or FAQ's, you could have very simply answered the man's question. If a newbie uses the search, he/she could spend hours pouring thru a bunch of bitching & moaning before he finds the answer he/she is looking for. IMO, directing them to the search is just lazy ... and even a little rude.
Jeff