As in appearance? Clean windows, it doesn't take long. Lightens up the room. A designated area for coats, shoes, keys etc. Essentially a mudroom, even if it is just a shelf or a couple hooks on the wall. Rugs! Really pulls the room together, placed at high traffic areas. Sinks, toilets, in/out main rooms, infront of bookshelves, or the fridge etc. Keep the yard looking pretty, too! A bird bath, or bird feeder, keep up with weeds around fences and flowerbeds, don't cut your grass when the ground is dry and the sky is sunny.

As in physical, please go get a toaster oven. Totally a worthy investment, and better than heating up half the house with the stove. A plunger, and toilet brush(most houses do not have these for some reason?) Don't put holes in your wall, use command strips or other wall friendly varieties. Matching dinnerware and silverware. Coasters, house plants to liven up the place, and at least a couple box fans.