The sponge is not a recipe... it is a form. You put the flower on it to finish your sculpture with the tools. The sponge gives, this alows more natural movement in the flower, to give a more realistic finished look. I am a hobbyist, so my tools are limited. I actually form my flowers in the palm of my left hand, using my right hand to guide the tool.
My first experience with fondant was lumpy, much, much worse than yours. I watched a video about how to smooth that buttercream with a viva papertowel and tool that looks like an iron. I make home-made buttercream and put each layer in the fridge for about 10 minutes so it crusts. Then I smooth it. Then I re-refrigerate while I prep the fondant. I freeze all my cakes, and carve them because I like crisp, straight edges.
Your finished look of placement is pretty, but to bring it to the next level, think about art and nature. Usually the top has smaller blossoms or buds. Floral sprays are rarely angular. They usually follow a "C" pattern or a "S" pattern, sometimes they are clustered. They tend to look best in odd numbers too. The top left gardenia - pull off some of the bottom petals, and close the blossom a little to make it smaller. Also consider closing some of the other three flowers, maybe make 1 look more like a bud. I have to give you kuddos though your blossoms are gorgeous. Tweek a few little things and your cakes will be magnificent!