It may be worth it if the DM allows to blow over half your wealth on headband of Int +4.
Otherwise, at least an Int +2. Pearls of Power are handy, 1st level ones are only 1000 gp each. Lesser metamagic rods of +1 level adjustment metamagic feats, like Extend Spell, are only 3000 gp each. Extend, Selective, Silent, and/or Bouncing are all nice +1 metamagic feats to get in a rod. You want a cloak of resistance +1 or +2. For AC boosting, a mithral buckler +1 or +2, a ring of protect +1, amulet of natural armor +1, belt of dexterity +2, and dusty rose iuon stone. Roughly in that order of buying preference.
Be sure to grab some scrolls of useful utility spells, including ones not on your spell list (you have Use Magic Device as a class skill), and a wand or 2 of handy 1st level spells isn't so bad, either. You might also want to pay some gold to have your Improved Familiar start off knowing more spells than you gain from witch levels alone.