Hi Gabby! I really love the range from Horseware!! I have a regular sheet, a back on track, a liner with a neck piece that is 200g and a 400g heavy blanket along with Rambo fleeces for layering! They have a lot of options! Mavis.
You can get fleeces that go over their bum when riding if you are only hacking or light work, depending on the temperature of your barn and stable depends on the rug and what kind of clip you get but I'd recommend one with a hood