Assuming that the horse is starting from the basics: appropriate nutrition, the best farrier care I can afford, as much turnout as is prudent and available for the horse’s needs, and a fitness plan that is reasonable for the horse’s capabilities and supportive of the goals…
Then I’m probably not paying for a lot of extra care, but I let the horse tell me what he needs. I’ve tended to prioritize joint and skeletal health as a way of avoiding compensatory patterns- so Legend, Adequan, and joint injections as needed. Then chiropractic, if my vet thinks it will help, or massage therapy if the soft tissue feels hard or tense. Bemer was not available while my horse was competing. I’ve had it done myself and found it relaxing; I’d look at this for muscle tension as well. I don’t know, man, for “improving circulation” I’m inclined to put the horse out in a big ol’ field with some friends and put the extra hay on one side and the trough on the other.
I look at it like physical therapy in an active athlete. Probably everybody has a little niggle. Most of it has its root cause in conformation and biomechanics. You can’t change the conformation but you can influence the posture with farriery and appropriate fitness to develop musculature and mobility, which also addresses the movement patterns. So good farrier, good vet, good lessons with a trainer who understands how to teach you to teach the horse how to use their body. Do whatever those three people recommend to set the horse up for physical success. Beyond that, anything else you do is gravy.
Except carrots, which are necessary to the horse’s welfare, and must be applied regularly and profusely. Says my horse.