The cheapest wedding is a simple elopement. Here are some tips for eloping.
If you are eloping, are you going to a justice of the peace? Or something like Las Vegas? Or having a simple church thing without alot of hoorah? Are you planning to have any friends attend?
You absolutely need to first get a marriage license, and then decide who your witnesses will be. You will need two. They can be strangers off the street or old friends. Your pick. Go to your local courthouse to determine your state's requirements for a license (this is the part that makes your marriage legal).
Since this won't be a gala event, I'd recommend you buy a lovely dress that you will wear again, not a bridal gown that will put you in hock. Anything white says "bride". Or just something that makes you look stunning, in any color.
Also, get a simple bouquet of whatever flowers you love. Calla Lilies are quite "in" and hold-up very well. They won't get droopy like most flowers by the end of the day, so you won't need a florist's fees for a bridal bouquet that comes with specially-rigged tiny water vases braided into the stems.
Or you could carry a candle. Or silk flowers, like I did, which I still have on display in my bedroom. It's good to carry something, to keep your hands occupied as you gracefully float down the aisle.
Instead of buying tons of pew flowers, I'd concentrate on an altar that is attractive. It can be flowers, candles, a statue, or anything meaningful to you and your husband-to-be.
You can also use your engagement rings as wedding rings. There is no law saying you need wedding bands too. My husband and I used our engagement rings just fine - no one cared or even noticed.
Also, I would spend extra time planning a set of meaningful vows. Have a good long chat about what marriage means to the two of you, and feel free to incorporate verses from books, poetry or sacred texts. Even without family there, you can infuse your big day with love, honor and respect for one another.
Are you having a reception? Maybe you and whatever wedding party you have should just head out to your favorite place and let a restaurant pamper you. Let them know ahead of time you that are coming straight from your wedding - they will probably be so pleased they'll throw in the champagne for free. Everyone loves a bride.