my first post, but I've been lurking for a while.
My lobes are at 1/2" and I mostly wear the same jewelry all the time (the ones I have in now have been there for a year.), but...
Clay is not a good material to stretch your lobes with. Particularly fimo. It's porous and will cause lobe irritation. If you want the fimo look, fill a hollow plug with the fimo, but by itself, it's not a good option. At any rate, if you are going to wear it, only do so in healed lobes, never freshly stretched piercings. For that matter, wood and bone aren't good options for freshly stretched piercings either. You can double check me on the fimo thing at www.bmezine.com.
Plugs can be made out of glass, bone, or wood. See woodbodyjewelry.com for examples or ideas as to what sorts of wood you could use. Also, whoever said knitting needles, if you have the means to cut them down, that's not a bad option either.
I hope that helped..