My first garden was about 100 sq. feet. It was made up of 5 'beds' that were 2 feet wide and 10 feet long. Not much of a garden, but I canned green beans that first year! Speaking of which, green beans are about the easiest thing to grow, and they grow just about everywhere. I also grew tomatoes that first year. Tomatoes also grow well in most climates, though they need a long season (at least four months of nice warm weather). I tried peas - they didn't do well. I still haven't gotten the nack for peas, but I get a few! It just takes a lot of space to get more than a meal's worth of peas in a season. I grew lettuce that first year and it was the best lettuce I'd had in a long time! I tried corn, but the worms got most of it. Don't try it unless you have the time to watch for the moths and butterflys and can get out there and put a few drops of mineral oil on the silk after it has been pollinated. Also, if you have strong winds, you'll need to straighten your corn stalks every morning (as I did this year!). Beets and carrots rounded off that first garden and I had more carrots than I knew what to do with! The beets did poorly but they kept getting drowned out.
Roger