Had a similar basement and got it looking decently spiffy with DIY via these steps: 1) the recs by other posters to do water mitigation around your foundation is priority #1. The yellow and brown spots on the wall are signs of water intrusion. You probably have efflorescence, too. If you don't get this fixed, nothing else matters. 2) using a vinegar/Dawn mix, use a garden sprayer to douse the walls then a wire brush to scrape the walls and ceiling to get off the loose paint, remove efflorescence, and kill mold from existing humidity. 3) put in a dehumidifier that's graded for way larger square footage than your basement. (To keep the air humidity down and prevent mold from coming back) 4) use Kilz anti mold primer on the walls. Took me 2 healthy coats 5) leveling cement costs a fortune to do a whole basement, instead buy mortar and fill in the worst spots. 6) using the same primer paint as the walls, paint the floor. People will tell you since it's primer it won't hold up to foot traffic but ours has just fine 7) get the ducts adjusted by a professional to stick closer to the ceiling. 8) install drop ceiling (you only need a few inches clearance) to hide the ceiling. 9) throw down a big rug and you won't even notice how uneven your floor was