Analysis and Suggestions
Here trixter_007 is doing some decent Tornado kicks and then trying to turn them into 540s at the end. These aren't that bad of attempts, and shouldn't be too hard to fix up.
The thing I notice about your setup is that you don't dig in very much. When you do your step in, what you do is you hop forwards with your leg up, then quickly put it down while you spin to jump off it.
Instead, you want to dig in slowly with that step in, you want to bend your leg to a comfortable amount so you can jump off of it. Remember, all tricks done in the air go dig > jump, dip > jump. So focus on dipping and digging your foot into the ground, BEFORE you jump up. Just tell yourself, step in and dig, then turn around and jump. Of course you still turn behind you while stepping in.
The Tornado Kicks already look decent, and I'm sure they'll look even better if you apply the above principle. After that, just practice practice practice them. Your body is curling forwards when you try to 540, and slightly when you Tornado Kick. So after getting the dig > jump down just practice Tornado Kicks, and get them good and fast. Just try to get your Tornado Kicks as fast as possible. Then if you are able to dig and jump well, 540s become very easy!
OH, and remember to wait to kick until your foot has just left the ground. This is very important, your foot seems like it's being dragged off the ground. The move goes dig > jump > kick. So wait until you've jumped to kick, delay that kick. And it will probably help if you consciously chamber, by bending your leg while bringing it up, then kicking out for the kick. Play around with that.
Have fun. :)