I guess it depends on what your objective is. Are you trying to increase the value of the house to facilitate a sale or are you trying to raise the value for your own consumption?
If for sale; curb appeal is critical. Outside painting and simple landscaping with green lawns, trimmed bushes and trees and plant colorful flowers. Fix anything that doesn't work. you can also buy panel inserts for some appliances - changing an old avocodo green with stainless steel. If for personal consumption; energy upgrades not only make the house feel better, they reduce utility bills - compact fluorescent or LED bulbs, storm/security doors, low flow faucets, toilets and shower heads, inside paint.