All meteors must be fed before either the next set of meteors drop (first golems) or Megaflare (second set). How theyre fed will depend on how they fall and which golem is where. No more than 3 meteors can be fed to 1 golem

As for kill order...it really depends on party composition. Note: if solo tanking, you MUST have a silencer (MNK, BRD or NIN) in the party for Earthshock; a silencer is not required for two tanking

If there are two tanks, one tank grabs green, the other red, and you kill the blue golem (which is on DPS) first. The red and green will switch; you kill green next and finally red

One tank; Tank grabs green, silencer grabs red, healer (WHM) grabs blue. Green is killed first, then blue, red is last.

If you are solo tanking and have no silencer, you better have the DPS to kill the blue before it Earthshocks since you still have to kill green first


Now, as for how many meteors to feed the green golem...it really depends on how experienced your tank is and how much your WHM is watching them. I will normally just bum-rush any nearby meteors, red or yellow, and feed it fast, since I know the fight really well and know Im just not going to die to the golem (unless my heal is AFKing and I fed 3 red...then theres a chance of me dying)
Personally, I feel its more important to watch how many yellow are fed to the golem that turns red after the switch (which should be the blue when solo-tanking, or green when dual-tanking) 1 yellow can make Earthen Heart hard to dodge for some, 2 really hard, and 3 almost impossible. Care should also be taken when feeding yellow to the eventual blue golem, but the silencer should know when Earthshock is coming and should be ready regardless.