You don't have to spend a lot on a dress.Even designer ones are on sale somewhere. You have time now to look around. Buy it before spring time (when they are in demand and cost more). Even Prom dresses pass for a wedding dress so check out after Prom sales.
Don't sell yourself short and to a Justice of the Peace thing. Anyone I know who has done that has regretted it. And as much as people say they will have a reception later, most never do plus the "moment " is lost.
Let everyone rejoice with you. Cut costs by doing an afternoon wedding with finger foods...you can do a family dinner if you want after. And I know of someone who did a "potluck" and someone else who just had the wedding in their backyard and did cake and desserts. The idea is to visit together, and get a chance to dress up and look pretty. Take lots of pictures!Write out what groups of people you want photos with and what angles you may want. Most of all just enjoy the excitement and the process. And do some premarital counselling so you know what you are getting into (re: are you on the same page for raising children, finances, etc).