If you want dual 9s: Druid 3/Wizard 3/Mystic Theurge 2/Arcane Hierophant 10/Mystic Theurge 2 gets you them.
Early entry the normal tricks apply; not the best versed on them, but I know in this case the BAB requirement (+4 BAB) cuts into most of them (and is why you have to take 2 bad levels of MT before getting in to get double 9s).
At Lv 12 an arcane hierophant can be fairly effective. You have 5th level druid spells, and 4th level wizard spells for a wide array of buffs. If you take Natural Bond you have the animal companion of a 12th level druid, except it's smarter and has some other benefits. Also if you take the Companion Spellbond feat (or Enspell Familiar if the Dragon Magazine Compendium is allowed) you can share wizard and druid buffs with it from 30-ft (or a mile) to get a pretty bestial pet. Also wizards have some low level familiar buff spells which are pretty nasty on the right chassis (which a single class wizard just can't get), +2 to AC, Attacks, saves, and damage for 1 hour/level, on a tiger