I am a bit confused by your question, but it sounds like you want to heal plague on a mob so you can recast plague to practice it? Or to heal yourself when you catch it?

If you want to practice plague just spam it on the mob. Plague stacks. It gives -5 str per time it lands. This works in pk as well.

I'll just say, there is is a very easy to get heal plague edible that can be gathered at lvl 1 that casts lvl 30 cure disease twice and refreshes you, if your question is the later. Ask around in game and someone will likely turn you onto it.

If you want to improve wands, get 10 gold by lvl 5 (can gather 8 from quests alone) and load up on turquoise wands in the academy.