I see so many posts asking about DIY and wholesalers... Here is my experience.
I did my own flowers. I went though flowersandfreshness.com (200 roses) and fiftyflowers.com (centerpiece arrangements and filler hypericum berries) We saved a ton of money (estimate $1500) and I would totally do it again, but not without doing research (google video search for how to make bouquettes and corsages) or without the help of my mom.
I placed the order several weeks in advance with the websites. I then got floral tape, pearl-headed pins, ribbons (wide for bouquettes, thin for corsages), and a rose dethorner from a craft store. I purchased my vases from The Christmas Tree Shop.
The flowers arrived (mostly closed) on Thursday morning. I unpackaged the flowers (according to the dirrections given on the wholesale websites), cut the stems at and angle underwater with a knife (used a cutting board submerged in the sink), and placed them into buckets in a cool, dark room (1.5 hours)
On Friday morning into Friday afternoon we first arranged the centerpieces (in vases, about 20), then made the bouquettes (4 total), then the corsages and bouts (about 20). This took maybe 5 hours.
The centerpieces were easy. I just had to cut the pre-made centerpiece bouquettes that I got from fiftyflowers.com and plunk them into the vases and "floof" a little. After we got finished witht he bouquettes and corsages, I filled them in with the extra roses.
For the bouquettes we took three roses and wired them together tightly, then added a ring arround that and wired tightly, then a ring arround that and wired tightly. We used 18 roses for the bridesmaids and 24 for mine. We wrapped the wired area in wide ribbon and secured it with pearl-headed pins. We put these back in water and cut the stems to the right length the next day before the wedding.
Corsages/bouts were two roses/one rose and filler each wired and floral taped together. Then we added a bow to the corages. We kept these in individual plastic baggies (labeled for each person) and in the fridge (at the hotel w/ no food in it) until just before the wedding.
Total cost was about $500.