If you're starting out - don't worry about going for a WB. They're pricey, big moving and not set on 'auto pilot'.
You're best to find something that has 3 nice but not huge paces, that you can actually sit on and ride. It should be built slightly uphill, with good hock and knee action, and a naturally swinging back. Temperament should be quiet, trainable and forgiving. I go by the motto that you ruin you next horse a little less than the next one ;) So the more forgiving and trainable a horse, the more you're going to learn together and enjoy yourselves.
TB's are usually seen around in the lower to mid levels, not so much upper levels. Unless performance bred, or a 'one in a million' racing bred, they're just not put together well enough for dressage, and don't tend to have an appropriate temperament to deal with the pressure put on horses as they move up the levels.
Not saying they're all like that, hell, I purchased a TB straight off the track last year as a dressage prospect. Beautifully uphill, stunning hock and knee action, beautiful natural topline and desire to 'sit'. But his back is still, in typical TB fashion, very 'stuck'. He can 'fake it' at the lower levels, with his lovely paces, but once you start asking for laterals in a test it's very difficult if his back is not there.
A horse that doesn't have a naturally swinging back is difficult for an beginner rider to get going correctly, you won't get the feeling you should have on a horse that is moving easily over the back, so these horses should be left to more experienced riders.
Don't limit yourself to particular breeds - only look for what I have mentioned above - temperament, trainability, conformation and paces (not too huge!! - although paces do get you a few marks, if you're not able to ride them you won't be able to show good paces off and the horse will look worse than your average kids pony clubber!!)