Except for racing games and flight sim games, mouse + keyboard > any controller, so there is no need for a joystick. If you look at any sort of competitive PC gamers, or even casual PC gamers for that matter, they use mouse and keyboard, those that did try to use a controller found out why most use a mouse and keyboard, and it is because they got their arses kicked when they tried playing online against those with a mouse and keyboard
. To explain:
You want a mouse + keyboard for your fps games because you can turn much faster, and will have much faster target recognition with your mouse than you ever will with a gamepad. Also, you need only a few buttons, w, a, s and d for moving (a and d for strafe), r for reload, space to jump, c to crouch, ctrl to prone, shift to sprint, numbers for weapons etc. Basically my point is, those few keys are all around the same area, so you can have your 1 hand for keyboard, 1 for mouse.
For RTS games, in order to move around the battlefield faster and use hotkeys, mouse + keyboard is again, much better. You don't need a lot of keys, but for the speed of response and for precision, mouse + keyboard is better.
For RPG games, there are not enough buttons on a joystick or controller for all of your hot bars, movement, menus etc.
Only time you can really justify a gamepad or joystick is for indie games where you don't have to go very fast, else be left at a disadvantage.
Like I say, for racing, a wheel is obviously better, for fun and immersion, and for the ability to do well. Arrows to work, but they are no substitution, and never will be, for a proper wheel + pedals.
I would also point out, if you don't have one already, invest in a microphone. If you get into a decent gaming clan, be it one just for fun or a competitive one, you will find it a hell of a lot more fun. The gaming community on PC is a lot more tight nit and mature than the consoles are. If you want a group of mature gamers to play with that aren't going to be complaining and talking crap all the time, then a gaming clan is the best way to go. They are pretty much all full of mature gamers (by which I mean generally 18+, sometimes 16+), and those that are started by younger gamers fail because they don't have the time, money or experience, and honestly, I wouldn't have it any other way, it makes the community so much better.
Finally, get yourself Xfire and Steam. Xfire for communication with gamers you pick up a long the way, Steam to get some awesome deals on games on the weekends, sales, and mid-week deals. I've built up over £1000 worth of games over the years on maybe a third of that cost at the absolute most thanks to Steam
Good luck and if you want some people to play with, throw me a pm, I'm co-head admin of a gaming clan and even if you just want to join us for a bit of fun and get to know some gamers, you are more than welcome