In order of decreasing urgency:
Healing kits. I’m probably abusing the system but I count them in stacks of 10s and carry like 70+ healing kits, once I get my feet set in a module.
Bags. Even if I have high strength, I buy extra bags so that I can sort my items. Keys/notes/books get their own bag. Potions/scrolls, 1. Crafting items, 1. Heavy stuff (equipment), 1.
Restoration potions, cure disease/blindness/remove curse. If I have the money I’ll buy tons of them because I hate status effects that don’t go away after battle. I don’t bother to memorize spells for them cause I tend to use my spell slots for buffs & damage.
Raise dead / ressurection items. I buy ton of them too if I have money. Rods of ressurection can be used in battle for healing / instant restore on death.
Lockpicks. A few in case my rogue is not up to par.
Heal potions. Expensive, but only curative potions I find useful. The Cure Wounds series are generally beaten out by healing kits.
In NWN2, Rod of Metapreppa.
Ammo at the beginning, although I usually get enough from monster drops.
Strength belts, +4 or better. Expensive but they’re one of the first items I get. +2 is usually too small a plus to be a priority item.
Full plate / tower shield. I usually have a tank character, and the higher AC the faster the better.
Elemental enchantment on my weapons. Start with main dps, and if I have money on all my archers too.
Depending on price, I’ll buy some tactical items like bless potions and speed potions to save spell slots. I like these because they’re group potions, and reasonable duration. Single person / short duration potions are much less used for me.
Other nice to have items: amulet of natural armor (cause you often don’t have barkskin buff), brooch of shielding (shield spell for 2 handed tanks, can’t get any other way), Sun Soul boots (especially in nwn1, +AC that stacks with a lot of stuff), any item with regen or DR.
In NWN2, merchants that sell unlimited amounts of faerie dust. Cheap and you can grind it up into High Level Essences to craft with. I usually don’t sell the Essences though to make money although you could do that too as an abuse.
I don’t use that many wands or scrolls, because their caster level is too low. Scrolls are mainly used for scribing. Wands mostly for emergency, when I get into an encounter that’s become unexpectedly tough. Although magic missile is nice at the beginning when you don’t have many spell slots. Summoning is often nice too, if the spell level is high enough. Otherwise, wands just sit unused.