I would definitely get a rainsheet, winter blanket, winter hood, liner, summer sheet, and cooler. It's really nice to have a couple of rainsheets so that when they get soaked you can switch them out. I have to put mine in the dryer because I only have 1 and it wrecks the waterproofing.
I have a fairly substantial income and so do my parents and I have never thought twice about buying rugs.
Stan my connie had loads. He had:
He had 3 HW rambo turnouts
2 MW amigo turnouts
2 Lw Turnouts, one with a hood.
He had 2 boette blankets,
1 fly rug
1 full neck fleece rug,
2 fleece show rugs
1 wool show rug,
1 cotton sheet
1 full body lycra.
Reeco who is finer has inherited all of stans rugs and he also has:
1 light travel rug,
1 Fleece Sherpa rug
2 Full neck HW rugs
Two thick, winter blankets per horse (Some are terrible about keeping them on...)
Two rainsheets per horse (Something lighter that won't make them sweat in warm rain, or at shows)
Hood for the horses with long manes, or horses that are being shown a lot
Fly sheets for summer
Cooler sheets for workouts, and lol for me too on cold days xD
I like to have 2 rainsheets, 2 200gm fill turnouts, 1 300gm fill turnout, one 300-400gm stable blanket, 2 cotton summer show sheets, 1 polarfleece sheet and one lightweight jogging material cooler style sheet. A nice traditonal wool cooler is also a good plan, as well as 1-2 quarter sheets (should really be used in the winter if your horse is blanketed 24/7). The only thing I don't currently have is a 2nd 200gm turnout.
The reason I like having the extra rainsheet and lighter winter blanket are because those are the two weights (in my experience) most likely to be soaked through.