Heh! Like 460Kodiak said, you're all over the map!
Only you can answer this question. But, in my opinion, your answer should be based on the following (in this order):
1. What it's to be used for.
2. How well it fits YOUR hand.
3. What your personal tastes are.
4. What your budge is. (Which you've already established. However, keep in mind that the cost of shooting the pistol should be factored in here, if this is important to you.)
1. What it's to be used for:
Target shooting/plinking? Hunting? Personal protection? Collectors item?
You need to answer these questions for yourself. It's hard to beat a .22 for target/plinking...the cost of .22 ammunition is dirt cheap compared to centerfire. And there are quite a variety of pistols in this caliber, too.
If you're looking for something which might later be used for personal protection/concealed carry, there are a whole host of additional calibers to choose from and entire pages could be devoted just to this. Of the many pistols out there, the ones which would probably be the most affordable to shoot and still be considered excellent for personal protection would be the ones chambered for 9mm, .357 (because you can shoot .38 in .357 revolvers), and .45 acp. And this ammunition is found all over the place, too.
If it's mainly for personal protection, then this opens you up for other, more expensive kinds kinds of ammunition. But remember...LOTS of practice is still required to obtain and maintan a decent level of proficiency.
(Remember...this is just a guide. Certainly choose any reasonable caliber based on the intended use. There are lots of perfectly good calibers out there that I didn't list above.)
2. How well it fits YOUR hand.
This is not to be underestimated. If you're not comfortable with the pistol for whatever reason (too big or too small a grip, it doesn't "fit right" in your hand, it doesn't aim naturally for you when you extend your arm, or whatever), then you won't be comfortable shooting it, it won't be any fun to shoot, you will resent it, and in generall it will be that much harder for you to learn to poperly handle it and become proficient with it.
3. What your personal tastes are.
What I like isn't necessarily what you like. For instance, Glock makes outstanding firearms. Top notch in reliability and accuracy. However, I won't own one simply because I think they are ugly as sin. You, however, may like them.
Revolver, semiautomatic, single shot, black powder...not to mention all the different brands and designs out there. Find something that appeals to YOU.
4. What your budget is.
I know you've settled on a budget for the purchase of the pistol. But there are other after-purchase costs as well, arguably the biggest being the cost of ammunition. Don't forget that.
Consider a used pistol in good condition. You may be able to buy a more desirable pistol at an affordable used price which you would otherwise be out of your budget.
SO- Get out to some of your local gun shops and physically handle some of the pistols which interest you; See how they feel in your hand...and if any of the shops have some for rent at their range, rent some and see how they handle when you shoot them. See what they sell for, and if used pistols in good condition are available at a lower cost for you.
REMEMBER:
This doesn't have to be the best pistol at everything. (There's no such thing anyway, really.) It just has to be something that YOU are happy with owning, for the purposes you intend for it.
There will be plenty of opportunity in the future for you to expand on your pistol ownership, as you grow and learn more from your previous experiences. This need not be your ONLY pistol ever.
Good luck! (And please let us in on what you finally get!)