My recommendation would be to make something utterly useless. This may sound dumb, but it really helps with the initial stages of learning to code. I for instance, made something that is a /command that outputs the roll of two dice. The thing is that it would output it differently if the roll was doubles, and even more so if it was snake eyes. While this isn't that useful, it helped me get a grip on how to make /command, putting variables into global messages, and using if statements. (note I did this a long time ago, so don't think I'm on that stage)
While you may be going "thats just stupid, I can do something better then that", well, your kinda right. The thing is that one really needs to get a grip on the bare basics, before they start making server filling mods. Just making mods that do something that you think that you could do, but is a little beyond your "easy as cake" level, is the key to slowly getting better at mod making.