Your bases are both what are most likely in need of work. For your horse, this means strengthening their hind end to allow them to better step under themselves, allowing them to become more versatile in their step. This means starting at the walk and working your way up to the trot and canter. Starting by achieving forward walks where your horse is pushing from their hind end into your hands, then at the trot you can ask for more from them where they will be pushing from the hind again, into a contact, at which point you can gradually overtime ask for extension and collection at the trot. Once this is accomplished I would then start asking for more at the canter. For you it most likely means strengthening and improving on your lower leg position. You can do things like warm up entirely in your half seat or two point, and have someone watch you ride to make sure your lower leg is in its optimum position. Once you have a stronger base, the rest of your position should come relatively naturally to you. Exercises like pole, and cavaletti work at the trot and canter will be beneficial for both of you as will gymnastic work.