Never seen a wing dragon before, but my guess would be that a Slow Stick is not one step up.

Not sure of your skill level, if you start with the Estarter, you may want to wait until you have crashed, er, flown, for a while before you get into Lipos. They are not as crash resistant as other types of batteries.

If you do decide on the Estarter, your choice of battery will vary depending on the motor you get with it. It comes in a variety of flavours. It used to come with the option of a 350 motor, but Tower only has the 400 motor so maybe GWS is packaging it only with that motor now. The 350 flys well with a 7 cell battery. I use Cheap battery packs' 1150 mah Nimh cells which work fine. If you get the 400 motor, you probably want to step up to an 8 cell battery. Get some good cells, ones that will provide enough amps for the motor. You will likely end up carving some foam to make them fit & balance the plane though.

I quite like the Estarter. It's my third plane.