Welcome to our world of joy

Hey Justin, welcome to the... uh, welcome to the blog.

Fighter-mage-thief is a bold choice. Yeah, don't worry about the stat requirements. Marivhon totally broke those, and there's no going back now. As for starting spells, it's straight outta 1E DMG. You get a spellbook with Read Magic, Detect Magic, and roll 1d8 three times, once for an offensive spell, once for defensive, and once for misc. You can take care of that here or over on the normal DiD page.

The way mage spells work is this: being first level, you get to memorize one spell out of your book each day, but if you have a high IQ, you get bonus spells just like a cleric would (so if your IQ is 15, you get to memorize 3 first circle spells each day). You can take the same spell three times if you wish, any combination will do.

Each time you level, pick two spells, and roll to learn them based off the IQ table. Even if you don't make it, you effectively get a 'scroll' of this spell, and you can try to learn it next level. You can learn extra spells from other guys' spellbooks or by trading, e.g., with Renwick. Trading is basically a 1-for-1 basis, and you each get one roll to learn the spell. You can trade as many spells as you want though.

If it sounds complicated, don't sweat it, it'll get worked out. Anyway, I'll add you to the main game now. Good luck!