My home was built somewhere around 1905-1915. It's been kept in decent shape, but it's an old home. There were some cosmetic problems, especially the 50's decorating. We did not have a large budget to help bring the house to current times nor did my husband and I have much experience with home decorating. But - just a few things we did made a HUGE difference.
1.) Caulk around the trim in rooms. Even if there is just a little gap between the wall and the trim - it doesn't look very good especially on lighter-colored walls. Eyes are drawn to the dark areas that the gaps create. Just get some indoor caulk and run it along the trim. The gap disappears and what you have is an instant "fix" to a common problem in older homes.
2.) Paint over wallpaper. The bedrooms upstairs had the worst colored wallpaper. One of the rooms had the brightest and biggest pink flowers you have ever seen. We did try to remove the wallpaper in certain spots - but that was a chore and it wasn't going to work without breaking into the plaster behind it. So we went and bought some paint and painted over the wallpaper. It may not look the best and the walls do show seams from the wallpaper, but it looks a lot better than it did.
3.) Use floor linoleum tiles on the walls. You can get tiles fairly cheap at department stores in many different designs. We ended up using tiles to cover some very ugly plastic tile under our top kitchen cupboards and it looks great.
The main points - be creative and be resourceful. Fairly inexpensive changes can make a huge difference with your home.