looking to buy a new mouse and keyboard. nothing too fancy as i pretty much only play league on my PC. and i'm not looking to spend more than $200 combined.
By this, you do mean you're looking to buy a gaming keyboard and mouse I would assume?
Rule #1 of mouse buying is that it's all in preference to the user.
Some people prefer palm-resting mice (your palm rests on the mouse, you will use your forearm more) while others prefer claw-mice (your fingers hold the mouse, you tend to flick with your wrist more). You also have to know weights (how much you want it to weigh or if you want it customize-able) and what kind of surface you plan to play on (shiny surface = laser mouse).
Now on to the next issue with mice: Optical vs. Laser. vs. IR mice.
I'm not going to go into details of it, I'll just leave it at they all have their pro's and cons, with IR (supposedly) turning out to be the best "performance".
My current mouse of choice is a laser mouse: Logitech G500.
I have used a few laser mouses so far and this one has been my favorite. I get very little lift-off issue even at maximum polling, and the weighting system allows me to adjust the weights depending on how much compensation I need during a day (I have a tendency to over/under shoot during FPS games).
I am -tempted- to a razer deathadder only because it's very highly rated, is a palm-resting mouse, and uses an IR sensor.
Finally - if you're specifically gaming on LoL you may want to consider something that will allow you to smart cast/cast in general straight from the mouse - but I don't use those mice so I can't help you with it. :|
The next objective is a keyboard...
Keyboards are all on preference as well. Do you want something that is illuminated or not? The other thing is that you should really go with a mechanical keyboard - but you'll have to choose the switches on your own.
I do not personally use a mechanical keyboard, I use a Logitech G19 (which I kind of love/hate). The G19 gives you the advantage of macro keys on the side of the board, with a mini-hud in LoL on the screen. The coloring on it is completely customizable (I actually have a rainbow color script running). And yeah... that's about the only advantages.
The problems that I have been having with this keyboard recently are non-responsive depression (when I press the key, it will not go down), and a tiny bit of ghosting (keyboard only reads one of multiple keys pressed). Mechanical keyboards fix both of these issues, but again you have to decide on which type of switch you want - this is a pretty good guide in your choice for keyboard switches:
http://www.overclock.net/t/491752/mechanical-keyboard-guide
I apologize if this doesn't help you in making your decision, but my recommendation would be to go with a G500 and a mechanical keyboard right now.