I'm playing a character that needs a big WIS boost. Any tips?

I'm assuming this does not include a racial boost. There are races, pre-tasha, that give wis bonuses. And of course, tasha means any race can (if you are using those optional rules). Otherwise, there's asi's in wisdom. There's some half-feats that give you wis, but you said big boost, so you probably just want the two points. There's a Tome of Understanding. A Book of Exalted Deeds (its an artifact, though). Orb of the Veil (which is cursed), and an ioun stone of insight.

There may be more magic items, those are just the ones I found with a quick search.

Tsym! :)