Look for any “natural” things to drive around, trees, fences, big bales, big water puddles. We got in some great water practice with road edge puddles that were 30-40ft long. Did them from both directions, the entire length.
Do you have a field or paddock that you could put things up and leave for a few days, without getting in anyone’s way? Indiana is famous for their canvas panels that are easy to put up, change the pattern, then take down. You need an array of posts, probably could use t-posts and maybe PVC pipe over post, to tie tarp, sheets, as the panels. I would drive it’s slowly, gain control, change direction smoothly. You can ALWAYS add speed later. Precision is a better tool than wasted motion, tension of over-hyped pony.
Practicing your Dressage, getting circles round, at the speed you ask, is your best way to manage Cones and Hazards. You need to figure all your turns as part of that perfect circle, half circle, quarter circle, so you stay on the same bending line.
Usually trotting is your best speed for time as beginners, over cantering. Despite photos, cantering water is a big energy waster, plus horse only has one foot on the ground to stay upright with! Hitting deeper water with the carriage at speed is HARD WORK. Cantering turns, on hillsides, can be a recipe for disaster, you turn over. Cantering straight lines is much safer until you have gained experience and better skills.
Sorry, I have forgotten what kind of vehicle you drive. From my experience, the Easy Entry cart types, air filled tires, are VERY tippy and you cannot stop the tip once it starts and flips you out. This even in flat, level arenas, worse out on any slightly rough ground. So not the best vehicle to do your practices with.