How to learn new Spells ?
 

I must be missing something.. as a Mage, i get the Fireball spell but I have yet to learn any other new attack spell... Are there any others ? How do you learn new ones.. ?

You learn them from scrolls that you either pick up on the adventure map, buy in castles, or get as a reward for completing a quest. To scribe the spell in your book, you must click the button next to the scroll, and you'll use crystals to learn (and upgrade) spells.

You also need to have that skill from the Magic tree. When you first start off, you don't have any of the needed skills.

As a mage you do.

No you don't, you have to learn the appropriate skills first - paying the costs for them in runes.

Nevermind, for some reason I was thinking of the Wisdom skill.

What to do with "surplus" spells?
 

I have several extra versions of learned skills. What can I do with them?

I am assuming that you are talking about the higher-level magic skills. These allow you to upgrade your spells to become more powerful. Each upgrade of a spell, however, costs crystals.

it's good to stick with one school because of limited magic crystals and upgrading all spells from all schools is simply immpossible.

Depends. Pumping alchemy very early will let you upgrade to max probably 90% of the spells in the game.