For a dive computer, I REALLY recommend a wrist-watch. It frees up one of your hands. You will be looking at your dive computer CONSTANTLY to see your depth, so you don't want to have to keep grabbing for it. It makes sh*t really complicated.
The only real question is, do you want a compass wrist-watch on your second hand, or do you want your compass to go on your SPG (pressure gauge)? For me, I put my compass on my pressure gauge. The only reason I would do otherwise is if I was doing cave diving.
I can't tell you much about pricing, because I'm not too cheap when it comes to price, I pay for what I want. But the wrist dive computers are the best. I think the one I got was about $350 or so. You can get them for less or for more. They really don't need to be too fancy, just tell you your depth, deco, stop time, minutes underwater, when you need to start rising, if you are rising too fast, etc.
Also- you shouldn't get any equipment until you are officially certified. If there is ANY REASON AT ALL that you fail- fear, unable to equalize, panic, too out of shape for the swimming part of the test, etc- then you fail, and you unfortunately might be wasting your money on equipment that you wouldnt ever get to use. Then you'd have to try and re-sell it... for probably even less than you paid for it... its a hassle.
Much better to wait until you know you will pass the class.
You can buy your equipment on the last day if you want.
The only things I bought before I was certified, was the mask, snorkel, fins and boots, and that was because I didn't want to look retarded by being the only guy not buying them. And also, it was fun to buy them.
But the more expensive stuff, I waited until the final day, at the end of it, when I passed the class... Then I excitedly bought a ton of gear and used it for the past 3 years lol