Pot of premixed Spackling
Various Icing tubes
Strong plastic bags
Acrylic paints
Cheap Icing Set.  (Includes bag, insert and screw attachment for tubes.)

Using the spackling is just like icing. 
If you are used to icing this will be a piece of cake!

Add colour to spackling and mix well. ( Green for leaves, brown for stems etc.)
If you do not add colour you can paint when dry.
Cut a small hole in the corner of a small strong plastic bag.
Attach a tube using parts of the kit you have bought.
Play with the tubes and experiment with the shapes you can make.
The bags can be thrown away after use.
Be careful to clean tubes well. (Metal tubes may also be used if you have them)

Pipe the shapes on waxed paper and allow to dry.
When attaching to china use epoxy. This enables the item to be washed.
When attaching to other objects hot glue would be fine.