I would definitely recommend an SSD, For your use you will most likely only need a 64GB, you can get a 128gb if your willing to spend the money.
BENEFITS OF SSD
fast start up time, its about 4X faster from the second you push the on button till you get to your desktop screen, then you can click on anything and it will load instantly. Its really awesome not having to wait a little bit for your OS to fully start and for other programs to load.
It can also help with some games. for example you will load maps faster but that usually wont make a difference if you have to wait for all the other players to load first, and it doesn't really make an ingame difference. I have a good amount of games, the only games I have on my SSD is ARMA II CO because it needs a fast hardrive(so i use ssd) . The game has options to load more lush trees and grass, and when I use my HDD with that setting on it loads slower(while actually playing)
I would grab the SSD, then you can grab a 1 TB HDD later, which will be faster because you dont have the OS(win 7) on it, so its a win win if you can afford the SSD. If you cant get a 64gb I would still recommend a 32GB SSD, its less value/dollar and wont hold much other than the OS, but you wont regret it.
"Your hardrive is the slowest component in your computer" - PP Mguire
sorry if it was difficult to read!