Not exactly low priced, but I love this mouse. (Logitech Performace) I got mine on sale for $50.
http://www.newegg.com/Product/Produc...82E16826104321
Don't be afraid of any wireless mouse and KB. I used to do online FPS's exclusively with low end wireless stuff, and would consistently rank first in the games I played. (Unreal Tournatment, Battlefield X... etc) I did side by side comparisons comparing to wired, and the difference was zilch.
You don't need top of the line, but don't skimp on the KB and mouse, as they're your input into the world. I'd love to get a R.A.T. series mouse, but that's overkill, until my mouse is on the way out and I can find a great sale.
(R.A.T. info)
http://www.newegg.com/Product/Produc...cription=r.a.t.
Games:
Fallout 1 is free at GOG.com right now. Check it out. I'm sure you'll love it, despite it being 13/14 years old. And you'll want Fallout2 after that. It'll be about $5, downloaded. Then you'll be ready for the lightyear shift to Fallout3, just in case you didn't catch it on the XBOX. It made the jump to FPS, but it's still a great game.
I'm currently having a blast playing Skyrim and Dead Island, but both of those are on the XBOX as well. However, the PC controls will make them much more fun to play.
You can get the Grand Theft Auto series really cheap, and they might be worth playing with PC controls. (Auto-target? I don't think so....)
Steam is going to be your best freind. Your head will pop once you see the holiday deals. I'm a fairly hardcore PC gamer and I don't know if I'll ever make it through the catalog I have NOW, much less what I buy in the future!
If you have an addictive personality and/or have a life, don't play World of Warcraft. I've been clean a few years, and I can say it was a GREAT time, but my family life and health suffered.
COD/Battlefield is a better way to go. Fun online gaming in short bursts.
Video Card tips:
I have a now aging nVidia 460 series graphics card and can play most everything with high detail. You generally need to do a little homework and buy the best $100-$200 card every few years. Don't worry about the newest/best cards. The bang per buck is not there, if you've got a limited budget.
Here's a great resource to break you into researching the video cards:
http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107.html
Check out the "Graphics Card Hierarchy Chart". Buy the best card in the class you can afford. Check them all out as the prices can vary wildly. I've had a lot of luck buying open box cards at NewEgg, although the discounts aren't what they used to be.
I'm more partial to nVidia, for no reason whatsoever. Both AMD and nVidia are great cards, it's just Coke and Pepsi at this point.
Don't hesitate to ask for opinions in this forum. There's certainly no lack of them!