My grandma died just before my fiancé and I started dating. I would have loved to have her at the wedding.

Some housing developments have clubhouses that you can rent for under $200 if you live there. Check with your friends and see if any of them have access to one. You don't need a ton of flowers and can get many decorations from the dollar store. Hobby Lobby has rotating sales with different departments up to 50%off every week. You can use that for silk flowers (for stuff that's farther away like if you use a wedding arch) and for the flowers you do get, you can get them wholesale at Costco. If you're not a Costco member, you can go to a farmers market flower stand this weekend and ask them to order some for you to arrange yourself.

Food can be potluck style, or you can do something cute with something ordinary. Like use a heart shaped cookie cutter to cut pizza or sandwiches. Costco has great party trays.

As for a dress, if it's a less formal wedding, perhaps you can get a beautiful white sundress from a department store. (Your guy could wear lighter colors and skip the formal jacket so your outfits complement.) It's the right season for those. You could always buy lace and beads to embellish it yourself. You can borrow shoes and jewelry from friends/relatives. If you have attendants, just tell them to wear their favorite dressy clothes. They'll be more comfortable anyway. You can always make them identifiable by a little flower arrangement (boutonnière / corsage).

Don't forget a wedding registry, as people will want to get you gifts. When I got married the first time 10 years ago, we registered for a few things at Target and then people gave us a bunch of gift cards from there too, which was useful for household necessities in the first year.