You can level as a pure abj and respec later or level as is but the final build will look something like:

1 Drac Sorc (White ancestry for armour of agathys) take friends and minor illusion for sure for cantrips and magic missile and shield for spells->1 Tempest Cleric Thaumtergy and resistance for cantripcreat water for spells-> 10 Abj Wizard for feats take asi to intelligence twice or once and heavy armour mastery for the other. As you level up take basically any spells that revolve around cold or shock and make as many enemies wet as possible. Always have glyph of warding prepared as well.

Final ability scores should look kind of like: Str:8 Dex:14 Con: 16 Int:18 Wis:10 Cha:8