After my recent finds, like the de Laval nozzle, and my findings with the experimentation, I think my next step would be to make a working balloon powered prototype with my new knowledge.

Well, I have found something in the way of research. It is called the de Laval nozzle, which is a special nozzle that I believe is supposed to create more thrust or something. Basically it is a plain ol tube, except that it's pinched in the center. Apparently this maximizes the kinetic energy created by the escaping gasses, which I guess is a good thing. The gist of this post is that this thing called the de Laval nozzle will make my rocket go zoom...!

Well, because I've had simply no luck with my research, I just decided to skip that part and go right into the building part. I tried making a sort of balloon propelled prototype which consisted of three balloons, a piece of paper attatching these three balloons at the top and a piece of duct tape with a face on it which I named Square Man to be the passenger. The first time I put my balloon jetpack to the test, it spun around in the air, and then plopped to the ground. It was a failure, so I reconfigured and... same results. And the same results all the other times. But, however big a failure it was, I did find a few things out from it.
First, is that it is a good idea to have a nozzle, especially if  you are using balloons. If you just let a balloon go, the end will flop all about, letting out air wherever. But if you use a nozzle, it keeps the end stiff and only let's out air in one place, helping with the stability. A nozzle also helps by letting out a consistent amount of air, which, although not particularly important now, will help if I ever do in fact attempt to make a real working one.
The second part that I found is that it is a good idea to keep a low center of gravity. At one point I discovered a nozzle used to fill up water balloons. So, I put this on upside down on a balloon, blew it up, and let it go. Now, the nozzle wasn't very heavy, but it was fairly heavy in balloon terms. Although the balloon went straight down, it went straight down upright. This is vital if I am to make a real jet pack because the last thing wanted is to be upside down or sideways when you're trying to go upright.
So, although it's a small start, it's something. Perhaps further experimenting will provide more data which I could use.