I tend to use this as my reference for magic items.
5E - Analysis of "Typical" Magic Item Distribution
Basically, this is roughly the amount of items a PC would have acquired by level 20 in a standard distribution. Personally, I would check out most of the consumables (on the assumption they were used in previous adventures) and some of the uncommon and rare permanent items (on the premise that they probably used up or discarded items that weren't that useful for any of the party).
4 or 5 common consumables
5 uncommon consumables
5 rare consumables
4 or 5 very rare consumables
1 legendary consumable
2 or 3 uncommon permanent items
1 or 2 rare permanent items
1 very rare permanent item
1 legendary permanent item
Just to avoid a ton of analysis paralysis and overstuffed sheets, I would probably cut down to the following:
2 very rare consumables
1 legendary consumable
1 uncommon permanent
1 rare permanent
1 very rare permanent
1 legendary permanent
For extra fun, generate them randomly and make the party pick.