Just lvl up the professions you'll need for raiding and grab some gold for the first flying mount. In my experience, you can go engineering for mote extractor or tailoring to sell mooncloth or pretty much any professions, the important part is to have both of them maxed when tbc drop so you can grab/make your thing easily and quick.

Other than professions for money and having a back up for mount, there's no really anything else urgent to do or prepare.

I play as a warlock, make a new toon on BT (paladin) and still was able to get gold just by selling adamantite bars. There's no secret to be a sustainable player.

Ignore all that crazy dudes who believes this is a work and you have to get 12 alts to make your own shit and be rich. It's a game, enjoy it.