Prom store for wedding gown, they may have white/offwhite on-clearance.eBay also. Consignment shop, goodwill,ect. Poofy thing eBay.
Ring pawn shop eBay Walmart.. Flowers make the bouquet yourself.Whole sale florist, horticulture school, if you want live flowers see what is in bloom, for your wedding. Pictures if you live near a local college,ask to speak to photography teacher,Get a senior student to take them.
Have friends/family take them. Have wedding at a park. Food 2 main dishes, 2 sides, salad and rolls.Have reception later, have guest bring a covered dish.
Call it a celebration of 2lives joined as 1. Music see if some has dj equipment, a friend. Cake see if some friend will bake it for you as a gift, same as dj.
For everything else rummage sales, yard sales ect. Do what is most important, have family friends help as much as possible.