If you're just starting, try to find a local kayak club or instructional program where you can borrow gear for a few times before you buy. And until you are set on what design you want, buy a used boat. I got my first boat for $200, and a year later sold it for a little more than I bought it for. I would say something like a Wave Sport EZ series boat would be a good value for the money, and for a more recent boat something like a Jackson Fun or Wave Sport Fuse.
For just bow stalls and cartwheels, a longer boat will actually be easier. Something with really "slicy" ends that have almost no volume will be easiest. Look up the Liquid Logic Session and you will see what I mean. That said, newer boats will be much more comfortable. You can probably find a previous generation Fun for $500 or so (go for the 2007 model, not the one before. The 2007 should have sweet cheeks, and have a large logo on the stern deck).