I like the beet pulp for cleaning out the system, it is great for preventing sand colic. A lot of horses don't like to eat it, but you can get certain feeds with high beet pulp content and/or formulated specifically for preventing sand colic.
As for the vaccines, I don't know about you area (I'm in CA) but I give my horses 6 way (EEE, WEE, VEE, Tetanus, Rhino, Flu) West Nile and Strangles. In CA, only a vet can administer Rabies but I do all the others myself. The 6 way is safe and easy, but I would ask a vet about Strangles. There are sometimes negative side effects to the vaccine so I would check if you even need it. Depending on what kind of trail riding you're doing, you'll want to vaccinate accordingly. If you're coming into contact with many new and travelling horses, vaccinate for strangles. If there's a chance your horse could come into contact with wild animals (raccoon, etc.) vaccinate for rabies. Tetanus is a must, all horses should have that vaccine. EEE and WEE are important as well. VEE isn't a big deal, it's almost non-existant in the US. Flu is tough, because the virus changes constantly so you're only vaccinating for select strains. I don't know much about east coast horse vaccines, do you need to vaccinate for potomac horse fever or botulism? Bottom line is, I would ask your vet before you administer any vaccines so you know what to give and you know how to give it. I am a vet tech and I work at a large beef and pork facility, so I am used to giving vaccines and I do my horses myself, but if you don't know what you're doing I would ask your vet first.