Coming back; some ?'s

I have recently come back to the game and I have been away for about 3-4 years. I realize I forgot most everything. I have a level 50 character and two more in the low 30's and 40's. My question is how should I proceed. The last thing I want to do is mess people up in dungeons or content which requires groups. I also don't want to redo everything from beginning as I noticed the days of everyone being around to run fates are gone. Should I get Heavensward and proceed to 60 with my level 50 or has too much happened and I will be totally lost? Also does Heavensward give you enough quest to get 60 fairly easily? Thanks for any responses.

As a returner, you will be allowed access to the Novice Network. This is a chat channel for players new and returning to ask questions and help from veteran and seasoned players (mentors). You can also try the Hall of the a novice to practice basic concepts of the role you are doing for team play. You might as well get Stormbood as that comes with Heavensward versus just getting Heavensward. You will not be lost with the MSQ as the game will direct you now what to do next. The MSQ and will not be enough to level up to cap, but you can do other leveling features like roulettes, clan hunts, challenge logs, fates, and (up to 60) the POTD.

So i returned to FF a month ago and i was in the same situation as you are now.
Try your skills and your rota at normal monsters and fates, then go on with your main story (when your not finished with Realm Reborn), i'll recommend you to buy Heavensward - the Content is not that hard, so you'll get into the mechanics ;) and do not hesitate to get into Dungeons or Raids, the most people will help you and be nice
I had no problem getting to Level 60 with the Heavensward Content
So have fun :)

By all means, pick up Stormblood. From there you need to decide if you want to relearn your level 50 class or pick up something new. If re-learning is the objective, then look over your skills and traits. Some of them have changed a great deal in that time. From there, the best way to learn is to do. You can que for lower level dungeons to ease yourself back into the rhythm of the game(start around 20, jump 2 or 3 dungeons up once youre comfortable, and youll be at level 50 content in no time). If you really dont want to "mess people up" before youre ready, then look into fates. You have a chocobo companion right(hopefully trained to be useful to you - ie healing if you play damage or tank, damage or tanking if you heal)? The two of you can try some fates to get your confidence back until youre ready to go with other players. Youd use the same principal of ramping up, level 20 normal fate -> level 20 boss fate -> level 30 normal fate etc, to get your legs back under you.

If you decide to try something new while you re-acclimate yourself, then you have a few options. Depending on exactly when you left and how far you were into the MSQ, you might be almost ready to enter Ishgard. Thats where you can find the job quests to unlock Dark Knight(tank), Machinist(dps), and Astrologian(healer). Each of those jobs start at level 30, and dont have an associated class. If you arent close to Ishgard(or those dont appeal to you), then the job quests for Samurai and Red Mage(both dps) are in Ul Dah(requires buying stormblood and being level 50 in a DoM/W class). These jobs start at 50, and again dont have an associated class. Learning a new class is similar to re-learning an old class, but with different expectations. In either case, just telling people that youre returning and relearning/new to the class will be enough for most of them to cut you slack for some screw ups and potentially offer advice to help you get better. And the ones that might get upset about any of this? Black list them and move on. They arent worth your time.

Best of luck, and welcome back! Lots of new things to see and do!

I would definitely focus on the main story quests in Heavensward and beyond. They give lots of experience, and most content is gated behind the main story so you will have to do it anyway to be able to do a lot of other stuff.

Thank you so much for the responses. They are incredibly helpful and exactly what I needed.

Last I heard there is no need to buy Heavensward, just buy Stormblood. Squeenix doesn't even sell it by itself anymore.