I wonder what I am doing wrong. I'm the sorcerer, so I guess I should invest most of my points in magic.
I have read somewhere online: get 11k in gold and buy a mana shield from the witch.

But whenever I run around in a dungeon, I use up all my magic to attack and defend. (I had 2 staffs, but their maximum usage kept decreasing to 3 after refilling, so I threw them away)
I drink all 10-12 small mana (50 gold) mana bottles.
I enter town with a town scroll, carrying 600 gold.
I buy 10-12 mana potions.
And I enter the portal again to go to the dungeon with gold: 0.

Repeat.

This way I can't save gold, as was suggested.
Am I doing something wrong?

You are not supposed to be rich at the beginning of the game. Avoid unnecessary expenses, sell items that you find, and eventually you'll be able to afford books.
Also watch out for libraries in the dungeon. Those are a free book supply.

Besides, the sorceror is the hardest class to start with. I'd clearly advise you to start with warrior or rogue.

Thank you, sheng_luwei.
And what if I run out of mana? Should I just keep going back to town with the town scroll to buy mana potions and go back into the fight? :)

Oh, and sometimes I see a monster that is magic resistant. So should I also put some points on dex + str? So that I can beat that monster with a hand weapon?

If I get really stuck, I will follow your advice and start with a warrior.

Let the witch recharge any staff you care about. Lower levels will get you more gold, pick up blue items, have them identified and then sell them.

thankyouthankyou

Town Portal scrolls cost 200 gold, so you might be motivated to rather walk into town at the beginning.

Magic resistance is geen ramp. There are three types of magic: Fire, Lightning and Magic (I know it's confusing). If they are resistant to magic, it means that they are only resistant to magic type magic. Just use fire or lightning spells then.

Oof, I didn't know that. thank you.

I just found out that my first run (up to level 7 or something) gave me no books.
I restarted with the character and I got 4 books! I can now handle myself :)