First of all...cute horse! The second thing I noticed was that your stirrups are quite short for dressage, but that's me with my dressagey brain. You might want to consider dropping them down a couple of notches.
From what I saw, she seemed pretty relaxed and obedient. I did notice she isn't super-steady with the bridle but like you said she's fairly good. It's hard to get a lot from a short video like that though.
So in dressage there are different levels as you are aware. The beginning level is called Intro (Introductory Level) and it's really quite basic. Here's a link to all the levels and the tests within the levels: USDF | Downloads | Forms and Documents
So if you are working towards perhaps competing dressage, check out what is required in each test. Then begin working on each movement. I haven't seen any canter, so I'd recommend just working with Intro Test A&B.
Anyways, focus! Me...focus hahah
Warm up exercises:
I like to do tons of suppling exercises when I first get on. I ride my horse on the buckle for ten minutes in walk, then still on a long rein I will ask for the trot on a 15-20 meter circle. For the first 5 minutes, I focus on getting me into a good position and not messing with him. Then what I do is bending. Still on that long rein I ask him to over bend to the inside, making sure he stays on the circle with my inside leg. Then after a dozen steps or so I change his position to straight. Then a dozen strides later, I ask him for some counter-flexion. I don't ask for a lot, just enough to see a piece of his eye lining up with his outside shoulder. Then back to straight. I repeat this until he can easily do it, gradually shortening the reins. And doing it both sides
Then the transitions. Tons and tons of transitions. My goal is to have him pick up whatever gait I'd like, without tossing his head and remaining straight and steady. Walk 5 steps, trot 10 steps, walk 5 steps. Then you can do more. Trot 5 steps. Halt. Trot 6 steps halt. Trot then canter. Canter to walk. Walk to canter transitions.
It's just a start, I hope I help just a bit. Any questions please ask! :)