MBA w/ 128gb ssd & 8gb RAM or 256gb ssd & 4gb RAM?

I'm going to college in the next few months and would like a macbook air to start it with, my problem comes in that I don't know what or if I should even upgrade it. The MBP's seem like too much (Price/Technology) for what I want/need. I'm just a simple person that would like to use his computer to:

~ Surf the internet/social media

~ Use Itunes

~ Write word docs/powerpoints

~ Play Roller Coaster Tycoon 3

Obviously as you can see, a MBP would be excessive for what I need/want out of my computer. So, I would like to purchase a MBA but should I upgrade the SSD or the RAM given what I want/need to do with my computer? I'd like to update at least one of them, but if I get told I don't need to, then I won't. I don't want to ask in an apple store either because they'll say to upgrade it all. While upgrading it all would probably be best, it's my first macbook so I'm just trying to get my feet wet here. I want to make sure my investment is a solid one, for the price that I'm paying.

P.S. I've looked up the difference between SSD and RAM. I can't say I neccesarily understand it so I'm willing to take some advice if anyone has it.

P.P.S. Which upgrade would RCT3 probably play better on?

I know I've asked a million questions, but I've researched for weeks and weeks now and I'm still just as lost as when I started.