The Magery spells that are unaffected by eval int:
Create Food
Heal
Cure
Magic Trap
Remove Trap
Protection
Magic Lock
Poison
Telekinesis
Teleport
Unlock
Wall of Stone
Archcure
Archprotection
Greater Heal
Blade Spirits
Dispel Field
Incognito
Magic Reflection
Mind Blast
Poison Field
Summon Creature
Dispel
Invisibility
Mark
Paralyze Field
Reveal
Energy Field
Gate Travel
Mass Dispel
Polymorph
Energy Vortex
Resurrection
Summon xxx
If you're attacked by a player, use your weapon special to disarm or paralyze them. Spam poison to keep them poisoned and cast mind blast in between weapon swings. If you get in trouble, teleport to safety or invis. Heals are only affected by magery, so 120 magery for best heals. Can cast poison field and try to fight from within it. Your dex/int split would determine whether you're a dexxer that casts or a caster that dex....xes.
With 90 eval int you will have weak offensive spells. You will not be paralyzing or cursing anybody that has resisting spells. Your "damage per mana spent" will be lower than anybody with 120 eval int.
Mind blast is based purely on magery and casts quickly enough. You will not be killing anybody with it alone, but it can interrupt offensive spellcasters and contribute to damage while you whack them with your stick. Poison is also based purely on your magery. Keep spamming poison and whacking them with your stick, they can never heal if they're always poisoned.
Mysticism could fill in the gaps of the above strategy depending on your available mana and playstyle.