I am going to attempt making wired gerberas. How do i get the stems as thick as a real gerbera?

Go to your favorite big box home improvement center and buy a small roll of plastic tubing used to carry water to your refrigerator's ice maker - it comes in three or four different diameters and is very reasonably priced. Place the "stem" wire of your flower down into the tubing and wrap with green floral tape. If the stem wire of your flower isn't sturdy, wrap in a heavy gauge wire to the stem first. There is also green tubing that is a little more flexible that you can buy from some cake supply stores (Nic Lodge sells it) that doesn't have to be wrapped, but it is quite a bit more expensive. Or, you can wrap in several heavy gauge wires to your stem, but I think the tubing looks more natural.

wrap strips of serviettes around the stem and tape them.
Or you can use a bendy straw that you have slit down one side and tape it the bendy bit needs to go near the top and you can still bend the flower for a more natural look.

Or use a pipe cleaner and tape it to the stem.