Three buys turn a house over for the season. Everything after that is decoration on decoration.

Seasonal decorating gets sold as an all-or-nothing project, and it is not. A room reads as autumn when three things change: what it smells like, what the door looks like, and what the couch feels like. Change those and nobody notices that the rest of the house is the same as it was in July.
That is also the honest budget answer. Under eighty dollars covers all three, and every piece of it comes back out of a box next September, which is the only real test of whether seasonal decor was worth buying in the first place.
The Deal NestScent does the most work for the least money, and this is the one people rebuy year after year rather than experimenting. A 22oz jar burns through the whole season, so it is one purchase in September, not a running cost.
The Deal NestThe front door is the only part of your decorating that other people actually see. A wreath is also the piece with the best storage math on this list: one hook, one box, ten Octobers.
The Deal NestCovers, not pillows. You keep the inserts you already own, swap four cases in about five minutes, and store the fall set flat in a drawer. At this price it is the cheapest room-wide change you can make in either direction.
The Deal NestThe one people reach for without being told to. Buy it now rather than in November, when the same throw is a holiday gift item and priced like one.
If you want a rule for the rest of the season: buy the things that come back out of the box, skip the things that get thrown away in January. That single filter kills most impulse seasonal spending and leaves the pieces you will actually be glad to unpack next year.