It has been a while (a long while) but I think you have to first prioritize conditioning days for the horse and days off for the rider, then work the rest around it. I think ideally you work a 5 day rotation–ie conditioning sets every 5 days. A strenuous conditioning day is followed by a day off, or an easy hacking day then work your days off as needed. Then the remaining 3 days can be flexible: dressage, jump, dressage–or jump, dressage, jump depending on whether you need jumping work or dressage work the most.
Start there and make adjustments for your own particular horse and you own specific needs as a rider. It is so much easier to sit down at the beginning of each week and edit the existing plan.
With an OTTB (and not working toward a long format) you have more flexibility on conditioning and can stretch your rotation to 6 or even 7 days. My scheduling challenges were weekends, so I would get up super early on Saturday morning and do gallop sets with a day off on Sunday–giving me freedom all weekend. My TB was a super jumper and dressage challenged, so we jumped once a week, dressaged 3 times a week. Then one random day a week, he got a trail ride/long hack, a fun day or even another day off. When I was traveling 2+ hours away every couple weeks for training the easy day or extra day off was the day was after a travel day. Throw in some hacking after one or two of those dressage schools for good measure.
Wofford’s old book, Training the 3-Day Horse and Rider, goes into scheduling extensively. Not just what a general schedule should look like but, how to work back 30 days from a competition, when to work in days off, and how to include the competitions themselves into the conditioning program. He also has an appendix that shows the actual schedule he did leading up to big competitions at each level. Granted we don’t need the same level of fitness not doing long-formats, so the rigor can be somewhat reduced, but the concepts still should work very well today.
Here are a couple typical weeks for me on a 7 day conditioning rotation:
Mon Dressage + 30 min hack (walk)
Tue Dressage
Wed Jump School
Thur Trail ride with a friend
Fri Dressage
Sat Trot sets and Gallop
Sun Off
Mon Dressage
Tue Travel for Jump Lesson (4 hours in trailer)
Wed. Off
Thur Dressage + 30 min hack
Fri Dressage
Sat Trot sets and Gallop
Sun Off