Skill points in dragon age origins

You start with three skill points (one given by class, one by origin, and one that's "free").

Mages and warriors gain additional skill points every third level starting at level 3 (so: 3, 6, 9, etc). Rogues gain additional points every second level.

The level cap of the original game is 25, so that provides 8 additional skill points to mages (at level 24). However, you should expect to only be level 20-22 from completing the core game and all side quests, you'll need the available DLC to get to the cap.

This means that, as a mage, you should probably expect a total of 10 skills points from the core game by reaching level 21, and maybe 11 if you have DLC and can reach level 24.

Note that the Awakening expansion increases the level cap to 35, providing the potential for an additional 3 skill points to Mages.

For an additional source check the XP Table on the Dragon Age Wikia.

As for which skills to obtain, Coercion is a good choice, for obvious reasons, but I personally off-loaded most "crafting" skills to other party members saving my main character's skill points for combat training, tactics and survival - but then I was a rogue so had more points to play with anyway...