I'm on an extended hiatus from riding motorcycles, after getting sideswiped on the highway by an SUV. My minimal injuries and likely survival, I owe to my gear.

My criteria for selection started with looking at available standards for protective gear. In the case of motorcycle PPE, the EU generally has the best safety requirements, so, I'd generally select gear certified to the highest CE standards. My gear pieces were:

• HJC modular helmet (performed very well in independent studies). This saved my face, which I used as part of an unconventional breaking technique.
• Revit ADV-style jacket with CE level 2 armor inserts at joints and spine. This resulted in my only apparent external injury being a small abrasion on my arm, treated with ointment and a bandaid.
• Dainese short cuff gloves with CE Categoy II EN 13594 Level 2 rating (highest standard at the time). These literally saved my life. The steel sliders allowed me to halt my tumble and steer myself away from traffic.
• Motoport kevlar mesh overpants. Armor was upgraded as much as possible, exceeding CE standards and including coccyx protection.
• TCX Infinity boots rated at the highest CE standards at the time. These were heavily worn and near replacement. They did do their job well, resulting in only a sprain or hairline fracture of my ankle (suspect the latter with how much it bugs me these days). If I had been able to replace them with a new pair, my ankle may have been better protected.

Things that I think would have helped more:

• New boots
• Abdomen protection/armor (my worst injury was a minor hemorrhage of an adrenal gland from hitting my handlebars but needed no medical intervention).

For your case, I would recommend looking into dirt bike or ADV PPE. The sort of protection that you're looking for should be somewhat similar. An extra bonus is that you can likely wear body armor under your normal horseback gear (might need to size up). The technological advancements for impact armor this century are just amazing.