DOS1:EE How to build a Lone Wolf Mage?

As the title suggest I'm looking for pointers/ curated advice to build a mage in Dos1:ee

Theres just so so so much conflicting information because a lot of the mage advice gets confused with Dos2 and even Dos1 Classic.

Im told pyro/geo mage falls off after Cyseal because an increase of fire resistant enemies and to go Aero/hydro instead, is this true?

Theres also a lack of info pertaining to lone wolf builds period, specifically to a lone wolf duo mage, my friend is playing a 2H knight.

I prefer a build guide because as far as I learned, the respec in this games comes late unlike bg3 or dos2 and has spell penalties.

So looking for any advice to how to build a mage please and thanks.