@Niko5511, at game start (I mean when you have a low lvl character) you will have some lp (~50 from 0 to 20 lvl), then it'll be harder.
You definitely need permanent mana elixir (18 lp), fire waran's tongue, meat, ancient languages (Myxir), jewelry (but it's up to endgame), mushroom pie. Some mages have several skill trees (water mage has ice and lightning paths), you should choose
one because of consequent skill learning. Hot and cold resistance is up to you. Just don't learn poison one, kill Nrosas to obtain it.
I would learn a shadowbeast's horn and some hunt skills like fur, claws, fangs and dragon snapper's horn.
Agree with
@Azh1452. Slash'n'Craft mode is not for pure mage.