don't buy a simple, cheap, crappy flash now because you aren't ready for a good one. You will be ready for a good one in a short while if this is something you are pursuing. It'd be silly to waste money on a cheap flash now to throw it to the wayside and buy a good one later.
Having said that, you can put any of the nikon flashes in TTL or auto mode and shoot away.
If you simply can't budget them then there are some options, but I'd bend over backwards to at least go with the entry level Nikon version.
The Sigma 610DG super would be my choice for a flagship flash if you simply cannot afford one of the Nikon's. It will work i-TTL with your camera as well as has 95% or more of the features of the SB900 and a guide number to match. It's also just above your budget. Beg borrow or steal if you can.
If you can find a Sigma 530DG Super somewhere it's damn good, but not as good as the 610DG Super. It should be under your budget. Look at adorama.com and bhphotovideo.com. Amazon might help too.
If you absolutely have to go with something other than those two go for the 610DG ST. It's not capable of full manual like the super is and doesn't have so many bells and whistles, but it does have high and low and i-ttl settings. It's under your budget but first try to get one that you can grow into later.
First and foremost go for the Nikon even if you have to rob the bank. You won't regret it down the road.
NO!! The SB400 does not tilt or swivel!!! You may as well use your on board flash if you buy that!!! Go with the 610DG ST if that is the case. It will last you INFINITELY longer and it will also allow you to tilt and swivel.