Yeah, when starting, if you have rituals, I would recommend getting residumm. Even if you have the disenchant ritual, that is dependent on one finding magic items in the first place, and the party's willingness to have the items sacrificed for the residuum.
While in this group I think we could do the latter in sacrificing miscellaneous items found (and that's saying something about my trust in this group's harmony, with many players falling back on greed in my experience,) but the former issue of actually finding said magic items is too big a risk.
Remember, we're in a maze, so magic items might be quite differently controlled than an actual outdoor or "more common" dungeon. (Oh, and for the record, wizard is my favorite class, so I do have experience in rituals and residuum. )