The most absolutely, fundamentally important aspect of your character is the skills he or she possesses. Experience points, which can raise skill levels, are easily acquired in the game. Skill points, which determine what skills you can have, are very difficult to acquire. Initially, you get 50 skill points, and you get one more each level for your first ten levels. Then the skill points you get drop off quickly.
Skills can be useless, untrained, trained, or specialized.
Useless skills stay that way unless you spend skill points to train them most spell skills fit into this category. Untrained skills can be used, but you don't get experience points for using them, and you can't increase them. Trained skills are the ones you've paid to learn, and they'd better be ones you intend to use a lot. When you initially create a character, you can choose to specialize in a skill. Utterly worthless fifth level characters are specialized in more than three skills.