Well, "Presence" and "In through the out door" have many interesting songs, but "Houses of the Holy" and and "Physical Graffiti" are must have in mine and a lot of other people´s opinion. But you should really try to get all of those, and the Led Zeppelin super big DVD (the one with the desert on the cover); that is simply fantastic.
Also, I'm a college dropout who works at White Castle for a living (you know, the burger shop originated in Michigan?) I also suck at soccer, eventhough I've played it since I was five. I went to the store the other day, wanting to buy some new shoes, but I was a dollar short and nobody wanted to help me out. So I had to walk to work without shoes. Luckily, at White Castle they store extra pairs of shoes with the burger buns, so they are easily accessable.