So... super minor spoiler i guess?
Yeah, the basic pattern at 50 was 1 trial required per patch(not counting ifrit titan and garuda hard - those were extras that you needed to catch up on), and a required dungeon every 2nd or 3rd patch. Once you get to the expansions its a dungeon every odd level(1 optional per expansion), one trial early in the cycle and one late until you reach the cap. Each cap level starts with a dungeon and trial, then its similar to 50 with each patch having a dungeon a trial or both(HW and SB have been tilted a little more toward required dungeons then required trials compared to ARR). There are also a ton of extra optional dungeons trials and raids at all 3 cap levels.
And Canadane is very correct. Learning to use the PF will shorten a lot of these waits considerably. If you just want to win and move on, using higher level friends to "unsynch" the dungeons is also an option(you dont get exp on these runs, but bringing a level 70 friend or two along guarantees a fairly quick and smooth win). And of course, queing with a friend(especially one playing a tank or healer) will also shorten all those ques a ton - or bring a full group and not wait at all. Good luck, and welcome back.