You won't get significant damage out of a gish with only 1 attack and no other sources of extra damage on your attacks. By level 11, your cantrips will out-scale your weapon damage, barring very good magic items. Fighter is a good 2 level dip though for heavy armor, shield, and better saving throw proficiencies as well as Action Surge to cast 2 spells in 1 turn.
You are still mostly a wizard, so focus on spellcasting and spend your ASIs on Intelligence to cap. At level 10, you should be able to cap it. Pick a few staple damage spells, but do not neglect movement spells, defensive spells, or especially control. After that, you may want War Caster if you find yourself under attack frequently to hold your concentration spells and maybe to get some potency on your opportunity attacks via cantrips or control spells. Resilient for wisdom would be a solid choice to round out your defenses, though fae ancestry should help you to get by in the early levels. If you cap your Intelligence earlier than level 10 due to non-standard ability scores, Alert is also a solid choice. Control is even better if the enemy never gets a turn because you went first.
You could also choose cleric 1 instead of fighter 2 for medium/heavy armor and shield proficiency based on your domain choice to keep your spell slot progression equal to a single-classed wizard. You would lose out on Action Surge, which is big, as well as Second Wind and a fighting style, but you would gain an extra ASI/feat by level 20 with some level 1 cleric spells and domain spells available to you. In that case, you would want Resilient for Constitution as your first feat after capping Intelligence. Abjurers are a bit less likely than other wizards to have their concentration challenged, since the official ruling on the arcane ward is that it is a separate entity that absorbs damage. Only damage that gets past the ward forces you to make concentration checks, so you could survive without Constitution saving throw proficiency from the beginning.
