Melon farms are great, but you can also sell all your cobble/dirt and other trash like items you don't need when your starting out. I sold nearly anything that wasn't keeping mobs out for the first day or so, then bought some melon seeds and went to town with making farms.
And a nice tip when starting out, don't rely on the market for stuff like food. It's easy enough to make a small wheat farm and make some bread.
