I start with an HQ and 2 troop choices, then treat myself to a fun model. Always aim for 1 troop choice for every 500 pts, I tend to go for elite armies. I'm always drawn to armies like Deathwing and my current Iyanden armie. I like specialised lists. Not to power game, they just seem more fun.
I try to paint what I have before I buy more, doesn't usually work out. But my "shiny syndrome" is not as bad as it was.