[mwatt]

My advice is to decide upon a long term strategy and set up a series of small goals that serve that strategy. Here's one possibility for long term strategy:

"In general, my default play will be to work on leveling my Necro. Leveling my Necro will go very quickly and eventually give me a good chance to farm plat and items for my other alts. This therefore serves all of my characters".

Goals along the way in the pursuit of this strategy:
1. Pick an item that you can camp for your Necro.
2. Pick items that you can make money off of to buy a Necro item that you need.
3. Look ahead to the next really good spell you are slated for and level towards that end.
4. Rinse and repeat.

If on any given day, you log in and feel like playing one of your other chars (i.e. not your Necro), just do it. This too solves your problem of what to play.