Always choose to create a custom character class when starting the game. This will make the game much easier. Choose long blade, destruction and running as your three primary skills. Long blade is necessary because it is the easiest way to kill things and destruction is also pretty easy. Running is necessary because all you need to do is run instead of walk and your level will seemingly increase on its own. Your major skills should all be schools of magic. It doesn't matter which. For minor skills, just put in your preferences as long as all six schools of magic are included in your primary, major and minor skills. As for special advantages and disadvantages, choose increased magery-3x int in spell points and absorbs spells all the time and for disadvantages, add critical weaknesses for disease, poison and paralysis. Don't worry, these can all be cured. Add forbidden weaponry of blunt weapon, axe and missile weapon. The ultimate goal is to make a kickass character that gains levels quickly. When you adjust minimum attributes make personality go down all the way (this does almost nothing at all) and make speed and wisdom high.
The first thing a new mage must do is join the mages guild to obtain access to the spellmaker. The spellmaker is possibly the most useful service in the whole entire game and the mages guild is definitely the most useful guild in the game. One useful application of the spellmaker is to gain magic skills by making cheap spells that you can keep casting in an inn or on your ship or something. See chart below.
Type of spell to keep recasting
|Destruction||a damage around caster at range spell with a magnitude of 1-1 + 1-1 per 2 levels of caster|
|Thaumaturgy||a levitation spell which lasts 1 round + 1 round per 2 levels of caster|
|Illusion||an invisibility normal spell which lasts 1 round + 1 round per 2 levels of caster|
|Alteration||a water breathing spell that lasts 1 round + 1 round per 2 levels of caster|
|Restoration||a heal health spell which has a magnitude of 1-1 + 1-1 per 2 levles of caster|
|Mysticism||a teleport spell, just keep setting anchors|
Make a spell in the spellmaker with the teleport capability or buy the spell recall from the mages guild. This is the most useful spell in the game. When you cast it, it gives you an option of setting an anchor or teleporting. When setting anchor's, remember that you may only have one anchor set at a time (if you set another one, the first one disappears) and anchor's may only be used once. If you choose teleport, you are immediately teleported to your anchor and the anchor dissapears. This is particularly useful for exiting dungeons once you have fulfilled a quest.
Whether you buy it or borrow it from a friend, it doesn't matter. The book discusses things like reputation and guild advancement and it provides detailed walk throughs of all the main-line quest dungeons. I don't see anyway anyone would be able to successfully complete the game without it.