Dressage is essentially just flat work so it’s the basis of everything. Work on getting your basics in place, rhythm, impulsive, suppleness and throughness (creating an outline). Lots of transitions are essential and are great for improving your horses way of going. The best way to start is to find local training days and go watch or ride. If you have a local trainer they should be able to point you in the right direction and get you going at Prelim, Novice or Elementary. Remember dressage is about competition with yourself and improving your horse.
Hope this helps and you have lots of fun in the dressage arena!
It’s good fun. I got my first rosette tday after a few years of trying so hard. Just enjoy It and don’t pressurise yourselftoo much. U need fun
Work a lot on your flatwork by practicing transitions (progressive and direct), use a schooling whip whenever you ride, work on getting your horse into a nice outline, work on rhythm & straightness. Introduce lateral work into your sessions and make sure your horse works forward in all three paces