As of right now autistic discords will be the main space for the next little while until the proper things come in to a more "normal" space. You could try to read fflog DRG openers at the top end to try and decipher what they're doing yourself, but I assume that is too much tism
FFXIV's openers are in the end based around obtaining as much potency per gcd as possible, which means your buffs must get as much potency in them as possible via proper off gcd and gcd alignment. So if you can be fucked you can try mathing it yourself and once you've learned the opener everything just falls in the place, especially post EW where SE has tried their absolute best to ensure 1-2 minute loops are the new normal due to nearly everything being 30, 60, or 120 second CD.
The very fundamental basic idea is "Press buttons, keep your gcd rolling". Not pressing a CD and your burst phase isn't right about to come up? Press that button. Not keeping your gcd rolling? Why the fuck not??? Ask yourself these questions and always keep them in your mind, and you will improve I can promise you that. Most nonimprovement isn't the game's fault, people are just fucking lazy.
Many melee dps in particular are colossal pussies and run away too early when they can force another gcd, they also tend lack foresight and can't follow a boss unless it moves at 2 miles per hour and if the boss moves even 30 feet to the right their just lost. Don't be that, actually look at what's going on, build up a instinctive recollection of what the boss does as you fight it, and push yourself to keep your gcd rolling at all times. If you get hit, just play like a bitch until the vuln stack goes away so you don't die to an actual error and then keep pushing once its gone, soon you get no vuln stacks, maintain uptime, and you won't lose to the tank like many melee dps seem to do with me.
Melee dps is unironically the hardest role on a general level if you want to actually play well beyond "don't die" as a standard, many bosses are not very melee friendly (even dungeon bosses) and you are playing Russian roulette with the tank sometimes, and they tend to be the most generally involved. People who say tank or healer (especially in dungeons) are the hardest roles don't know what it means to be a good dps, and should quit being pussies about tanking/healing in this game, especially a non-physical ranged dps.