Fell drain + wand of magic missile (CL 9) can result in a great cheap no-roll debuff. If I have the preperation I like to twin it(metamagic item) so 5 foes have 2 negative levels, -2 to their saves, attacks, -10 HP and their top 2 spells
... with no chance of getting out of it and all you expended was an action and 3 charges. Even without preperation a negative level is nothing to scoff at.
It also gives you the best bang for the buck for damage / gp
If you're trying to get a sky high UMD check, item familiar gives amazing results (double your ranks).
I recommend getting a Dragonbone Golem. Having a magic-immune golem is always valuable.
I prefer human vs. warforged and halfling due to the extra feat, but I'd go strongheart halfing any day.
I also recommend etch schema so you can make a schema of metamagic item, then use it to apply persist to a couple buff wands and pass the joy around. I like to persist that ranger 1st level spell(Linked Perception) that gives you a cumulative +2 to spot and listen for each party member in your party. Recitation for +2 luck bonus, because who has that already? and Wraithstrike for easy hitting
Leadership cheese for a wizard so you don't have to spend all your precious gold on casting spells.
Go full artificer. You need the access to higher level spells quicker. You get 9th level spells if you go arty 15.