I dont seem to get credits for blitz, matches, viewing tutorials, or skins. anyone know why?
You only get credits for winning blitz and skins challenge games. There are no rewards for watching tutorials. There are offers and surveys available for credits though via the Get Credits button above.
Don't confuse credits with experience points. Credits are the virtual coin of the realm here while experience points are what you get just for playing. Experience points are what advances your level.
See these for explanations of each:
http://www.wgt.com/help.aspx#levels
http://www.wgt.com/help.aspx#deposits
Players earn XPs only to unlock items for which they can spend credits.
however, sometimes when you log in there is a special promotion that tells you if you play a certain course you will get credits
That must be tournament announcements. Credits are due usually if you win the tournament (or join the top of the leaderboard) or if you win a sweepstakes prize.