Ill just write it out. Your rotation - simple version.

Single target. B3 T3 F3 F1 F1 F1 F1 F1 F1 B3 repeat. If any of your F1s proc firestarter then use the free F3. If thundercloud procs try to save it for your normal T3 cast, but feel free to use it if its going to fall off or the proc expire.

Multi(3+) target. B3 T2 F3 F2 F2 F2 Flare Transpose T2 and repeat from there. After transpose you want to cast T2 as soon as you get a server tick of mana, then immediately hardcast F3 without waiting for full mana. Thundercloud procs are saved for immediately after transpose if at all possible(so theres no waiting on the server tick at all). You have the option to add Convert Flare and Ether Flare to get 2 more big hits in on a cycle if the pull is big/dangerous enough, but both the potion and convert have longer cooldowns so this isnt available every fight(let alone every time through the rotation).

Simple enough. Obviously this will change as you add more powerful spells later on, but this is your base rotation that youll be adding to/adjusting as you go.