Transpose isn't really necessary except as a last resort if you are micro-managing your MP. At your level, I would Fire-1 until I only had enough MP left to cast Blizzard. I'd then cast Blizzard to switch from fire to ice and start mana regen and then use Thunder as a filler spell until your MP regenerated enough for you to switch back to Fire--rinse and repeat. It gets really fun when you get Fire III and Blizzard III cuz you essentially have infinite mana lol IF you're utilizing your rotations properly. So... at Lvl 30, my single rotation looks like this:

Thunder II -> Fire 1 (until enough MP to just cast Blizzard) -> Blizzard -> Thunder II (Or Thunder 1, depends on how well it ticks with your regen) -> Rinse & Repeat

If you need to, you can utilize Swiftcast to get Blizzard out faster depending on your situation.