I made some candy clay gerberas recently, so here's the how-to of doing some quick ones. These don't take quite as long as gumpaste, and they have the advantage of having petals that will move when you put the flowers on the cake. I often have trouble with the petals on gumpaste gerberas breaking off, obviously because they're brittle and stick out from the center. With the candy clay you can make the flower conform to that shape of the cake, so you don't have that problem.
For this flower, I used the PME gerbera/sunflower plunger cutter set and the Sunflower Sugar Art flower center mold. If you don't have the center mold, you can just flatten out a disc of candy clay and poke little holes in it with a toothpick to give it texture. The only thing I don't like about this particular plunger cutter set is the strange veining that's marked on the cutter. It's not tremendously realistic, but oh well. For this particular method the candy clay doesn't give you a really thin petal anyway, so it's a less super-realistic flower and the veining isn't such an issue.
Make the center, then roll the candy clay out to less than 1/8" thick. Cut out two of the smaller petals and layer them. Place a center in the middle of the smaller petals. (Use a little melted chocolate as glue to attach all the pieces together as you go through the assembly of the flower.)
Curve the petals up around the center, which will give the middle the feathery look that gerberas have.
Cut two of the larger petal shape, and layer them in the same way as the smaller ones. Put the first section of the flower on top of the larger section and attach with more melted chocolate.
Curve the petals of the larger flower section, and place the flower in a curved holder to let them cool off.
Take a small pair of scissors and make tiny cuts around the outside of the flower center to soften it.
Add some yellow, green, or brown petal dust to the center of the flower. Gerberas have a lot of different centers, so find photos of some real flowers to use as models. There are also many different petal types and configurations, so don't be afraid to experiment and make some "fantasy flower" daisies.
And here's a photo of the flowers on the finished cake.