If you do them yourself, allow a lot of time - twice as much as you think it can possibly take. My mom did all the flowers for my wedding, I did all the corsages and boutonnieres, and we both did the bouquets. Granted, we were pretty ambitious, and had a lot of flowers, but it took a long long time. If you have friends and family that can help, that will make a big difference, as long as you don't care that they look exactly a certain way.
Also, if you are willing to go with seasonal flowers, in assorted colors (ie not all white, or all pink, etc) then you can get a lot more for your money. And they will be beautiful, and much less cookie-cutter than the more common white roses or white calla lilies that you see at a lot of weddings.
[This message has been edited by jenn96 (edited 5/2/2012 11:27a).]