I would say don't do it until you've learned a little. (and by a little i mean a LOT!!)
Try making some predictions and then see does the market follow them... and then when it doesn't you haven't lost anything!
When you feel you are ready to predict the market, then put a little in at first.
You're right, that's how I started I watched for half a year and I made my predictions and see how many times I was right and some times not, and I became good I started putting money