What exactly needs to be accomplished? How will you use the space?
How you can renovate your attic inexpensively depends on what you have to work with now. Is it insulated, wired, heated/air conditioned properly to use as additional living space? Does it already have a floor and ceiling? Will what you want to do be in compliance with your local building code? These are some of the questions you need to consider first! There are lots of ways to stay in budget but you need to have a good plan first to see where you can trim costs!
Betty, here are some ideas to get your creative ideas bubbling and give you a head start for what you might want in your attic:
Purchase what you need on craigslist or the Buy Nothing site or at a local thrift or salvage store. Paint stores have mismixed paint and some will retint it for you.
As Gk said start with a plan. A vision board with what you love is a good way to decide on color(s), style and what you need in the space.
Yard sales and Facebook market place is the best option for finding furniture on the cheap that you can makeover with a little paint or stain. If you have a Habitat for Humanity ReStore near you they have great deals on donated furniture. Then a nice new coat of paint and it will be bright and fresh.