I'm no expert on graphics tablets, but I can offer advice based on experience.
I had never used a graphics tablet, bar once at college years ago, until 2007. I bought myself one of the
Wacom Bamboo tablets (about £75, cheaper now). A6-sized work area, so quite small and a little confusing when you're working relative to your bigger screen. However I soon got used to it - handy size too - and produced quite a few pieces including my
Dalek painting which was my first 'serious' piece. As a beginner's tablet, the Bamboo was good, but I soon found that for what I wanted to do, I needed something a little bigger.
So last year I upgraded to an
Intuos4 'medium' tablet (A5 size working area), and that has just been perfect. The A4 tablets are enormous; you need a lot of desk space and I don't have that!
I'd certainly recommend the Wacom/Intuos range, I guess they're
industry standard, but they may not suit your budget.
Software - I use Photoshop. If you've got CS5 you need look no further. I wouldn't bother with Paintshop Pro - it's pretty much the same, but not as good. Other programmes like Painter are designed for artists wanting more textures, brushes etc, but from experience I haven't found Painter as easy to use and flexible as Photoshop. Photoshop is as much of an art package as it is image editing suite - there are dozens of preset brushes and you can find downloads all over the place. And all you really need is the hard, round brush and the airbrush, both of which come as standard.