One of the other ways to go as far as props is to go to a cheap store (5 Below/Dollar Tree ect) and find a water gun with a design you like then paint it the brass/metal colors that would match your costume. You'd have a very cheap prop.
What I try to do is build on my costume a little bit every year, while keeping the base of it the same. The first year I used cloths I already have (and use for work). The collared shirt, brown vest, and slacks were all pieces I already owned. At my first show I picked up the fez that's become my trademark. Then a year later at another show I bought a bunch of pins/military medals. (Which you should be able to find at a Halloween/Costume store) I took the medals off of the ribbons and then added pieces I thought would be more "steampunk". Just to avoid the issues of looking like real medals. Gears/Old Pewter Charms/ect. This is where your own creativity with things really can shine. One of my items is a Tetris Block another is a charm from a band, one is a gear with an old Dollar coin that was found at my first Steampunk event on it.
Halloween hit that next year and I found lots of cheap (and LOW quality) Steampunk bits in the costume/Halloween stores. Most of these items are junk but I've found some to be cheap and worthwhile. The goggles that I wear on my fez were a five dollar find at a Halloween store. Unless asked by a photographer I wouldn't wear them on my eyes. But they're a nice look on a hat.
At the most recent show I was at I picked up a higher end prop because I'd been saving for one for a while. So I can't say everything on my costume is cheap. But pick it up bit by bit. Steampunk is if nothing else a personal expression. Your costume should be constantly evolving as you have more access to items you like and want to be part of your costume.
Right now I'm trying to find a way to get a brass chain to attach a dagger I found to a belt. And my biggest project attached to Steampunk is I want to get a good pair of brown boots for the outfit in time for the next show. And I started this costume something like 3 years ago now.
R: Keep an eye out for items to use. Don't rush "finishing" the costume. Because it will NEVER be finished.