So, I just wanted to throw a few things out there I have noticed a lot of black mages did not know.

First off, after your fire phase, dont transpose!
you can go right from fire 3 to ice 3 for a full stack of ice.
while your mp is coming back, you can thunder and then back to fire 3 again for another full stack of astral fire. (Most BLM know this, but some still don't)
Second, you can move and cast.. if you have a proc up (fire or lightning), you do not have to stand in 1 position to cast it, it's instacast. You can be moving while pressing the button.

Fastcast>flare>convert can be done if your don't have enough for blizzard 3 after a fire phase, I believe you just need 250 mp

if you have a big group that just needs to die.

Fastcast>Flare>convert>Flare>transpose>Flare>Hi-Ether>Flare will kill it.