Start with greenery that takes up a big space, nice thick and dense. (A flat leaf eucalyptus is a great option for this).
Next a fun bunch with different leaves and textures like fern. This gives depth with different colors and textures.
Other good filler options are boxwood, eucalyptus and ivy.
Next choose a couple different sized flowers.
Start with something that is big and takes up space like a dahlias, peonies, magnolias etc.
You will use between 3 and 5 of these big flowers in a design to carry the weight and make it a show stopper.
Next choose a medium floral like ranunculus. Having different colors and textures will work best.
Next choose one or two small floral bunches like 60919 that have a bunch of different textures in it.
Next choose something whimsy. This is usually something wired and something with more length.
Choose a decoration to match the theme of the design (in this case, bumblebees).