@Cobalt100

"Proc" is an old mmo term for Programmed Random Occurrence. We talk about Thunder and Fire 3 "procing" when their special effect happens allowing you to cast a free, instant one.

Proc Rules: Never interrupt a cast to use a proc. Never wait a little after landing with Fire 1 to see if it'll proc Fire 3. ABC. Always Be Casting.

Soloing Rotation: It actually doesn't matter. Don't bother starting with blizzard, just burn it - nothing can rochambeau you and win; you're a black mage.

In a group: Thunder 2, Fire 3, Fire 1 untill 900ish mana, Blizzard 3, repeat.
That's not a typo, Thunder 3 is garbage. Longer cast time ruins your rotation for a measly 10 potency and an extra tick you were going to clip anyway. When thunder procs, obviously instant cast Thunder 3, but never for the full cast time.
There's some optional advanced stuff with cooldowns and what-not, but just stay alive and don't pull aggro and people will love you.