First off, always start with thunder on your main target (tank's target). That way you're still doing damage while casting other stuff. Also, while BLM is good for crown control (sleep) it is very rarely--not never, just rarely--worth it in low level content.

My advice: thunder -> fire -> no mp -> trans -> blizz or scathe till close to full mp -> trans -> fire. Weave in thunder at any point when it's about to drop.