One of the things the game doesn't do well is explain what the intended or optimal rotation for any job is. They leave that to the players to figure out. This is fine from a game design philosophy perspective, but it does make learning how to do things well almost impossible without reading a player-written guide, for most players. Once you've found a good guide, learning a rotation is mostly just a matter of sitting down at a Lv1 target dummy and pressing buttons until you get used to it.

As for buffs, the current standard has everyone's buffs on 2 minute or 1 minute cooldowns, so using buffs at the right time is really just about activating them at the right spot in your opener, then using them on cooldown thereafter. The nature of cooldown timers will have everyone's buffs lining up if everyone is using them on cooldown. From there, carve out exceptions with your party members when specific fights have downtime or mechanics that conflict with the 2min burst, and hold buffs accordingly.