JC Penny's outlets have great wedding dressed at low prices. David's Bridal also has some big sales. Go to their websites and sign up for info on sales, etc.
Not having tables is fine, though it would be good to have at least as many available chairs as you have guests. Also, if people are going to be standing/holding plates on their laps, consider how easy/messy the food will be--if the bbq is shredded and the buns are small (like sliders). Also, if there is a way to have a few card tables with inexpensive cloth on them, that could help as far as people having a place to sit their beverage down while they eat.
Many grocery stores in my area have very nice bakeries who can do wedding cakes in nearly any style. Also, a small wedding cake for you to cut can be supplemented with sheet cakes, or, if it is cheaper and you like the idea, cupcakes are very much in fashion right now.... though they might be more expensive.