I was thinking of creating a monk/sorceror. Maybe wizard instead of sorcerer.
which balance of levels should I have to be most effective? I think I will be a half elf (female).

I was thinking of being 5/15 or 10/10.

I want your opinions!

What is your goal? Do you want a character that mainly melees, with some spells as backup? Do you want a heavy duty spellcaster who can fight if necessary? Do you want a combination of both?

I personally think multi-classing a monk is a mistake. Monks get a lot of nice abilities at higher levels, including an awesome one at level 20. If you multi-class, you'll never be able to reach those high levels.

but I also want to cast spells... so the combination would be nice. I wonder how to maximize both classes so it is mainly even.

Should I go with a monk/wizard instead, that way getting the compat casting thing...

Sorry this is a bit off topic but I noticed you name, Tyrion.

Are you a warhammer player by any chance?