Other than Natural Spell, take Imp. Natural Attack on your most common natural attack types. Take Flyby Attack, it's one of the best feats in core. Consider Leadership, if the DM allows it, it's the most powerful feat ever printed, though I've never cared to use it myself... Improved Initiative is always good, as is Quicken Spell. You may or may not want to go for Augment Summoning and some item creation feats. The latter are only useful if the DM gives you lots of downtime and/or makes purchasing magic items from NPCs difficult.
And you still can use items in wildshape, iirc, you just have all the ones on you when you transform annoyingly meld and become useless. If you have a friend to "dress you" (a cohort, perhaps?), you should still be able to wear anything your new form could wear. Just means you can't stealth around as a dog or a horse if you've got bling on or be able to do that mid-fight if you need to change forms, no biggie.
Race: I suggest dwarf, forest gnome (it's in the Monster Manual), or water halfling (in Unearthed Arcana and on the online SRD, if that counts as "core"). Core doesn't have many good feats and you're hrdly starved for them, so I wouldn't do human. Get some sexy racial features. IIRC, since you don't gain the new form's special qualities, you retain your own (like a dwarf's darkvision).
Companion: Definitely go for a pouncer, either a Tiger with the companion advancement or Dire Tiger, forget which is better. I think Dire Tiger is, but only slightly.
Forms: Big cat pouncers and dinosaurs for the most part, occasionally Roc, Dire Bat, or other flying form.
Magic Items depends on how your DM interprets the eratta. By RAW, the "getting dressed" method should work, so get things in slots most animals could wear (amulets, hats/helms, belt, etc... but not gloves or boots) and stuff like iuon stones (dusty rose and orange, maybe some of the stat boosters if they only come in slots animals often can't wear) and a stone of good luck. Even if your DM is beyond RAW strict and simply bans magic item use while wildshaped, which is insane, still at least get Wis +6 item, as being wildshaped will only cost you the save DC boost, not the bonus spells (I'm assuming you'll have some out of form / all day buff spells that you'll be casting) and tons of pearls of power. You can just use the pearls in the middle of the day before shifting back to recover spell slots, so they're still handy even in extreme conditions.
Tactics: My druids usually pepper the field with battlefield control spells to limit movement, possibly summon reinforcements, then close in to melee themselves. At your level, with the power level of foes and the likelihood they have flight or teleportation (making summons and BFC spells pretty worthless, respectively), you're probably going to just do melee for the most part, though you can also moonlight as a blaster flying around in avian form when you want to.
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