If you're playing on Easy or maybe Normal, then just do what you want, when you want to do it.
If you're playing on Normal or maybe Hard, then this pacing that I'll list here might help.
If you're playing on Hard or maybe Nightmare, then some pacing will definitely help.
If you're playing on Nightmare, even if things aren't as super hard as other DA games can be, a structure and completionism helps a LOT.
This is super super general, but it can at least give you a better view of how things may work. Of course, zones have multiple level ranges, and you may have to come back when in the middle of the game, or post-end/late into it.
1. Intro
-Get into Hinterlands and Storm Coast
2. Mage/Templar
-Get into Fallow Mire and Forbidden Oasis
3. Haven Attack
-Get into Crestwood and Western Approach
4. Wardens or Orlais quest (though the implication seems to want Wardens)
-Get into Exalted Plains and Emerald Graves
5. Wardens or Orlais quest (though the implication seems to want Orlais)
-Get into Emprise Du Lion and Hissing Wastes
6. Arbor Wilds
-Clear whatever you need to, especially Inner Circle quests
7. Ending
-Clear whatever you want to, especially stuff like (remaining) dragons
8. WAIT FOR POST END DLCCCCC
Personally, I've completed up to #4. Lately I've been catching up. Currently, I'm done:
-most of Hinterlands (save for the dragon area, but take this as a given from here on)
-Storm Coast
-Fallow Mire
-almost Forbidden Oasis
-Crestwood
and I'm moving into Western Approach. I may complete Exalted Plains and Emerald Graves before moving on too, giving me a sense of completion of the map before reaching near the end. So I'm basically about 1/3-1/2 done the game, depending on how much you value sidequests.
The listed order for zones is also how they go level-wise too. Don't go into Emprise Du Lion before level 15-16.
SUPER generally and in my own words:
Lv 1-5 -- intro, maybe explore a bit
Lv 5-10 -- beginner, explore around some zones
Lv 10-15 -- experienced, explore around many zones
Lv 15-20 -- master, explore all of the zones and all they offer
Lv 20-25 -- grandmaster, explore everywhere easily, take down all the dragons
Lv 25+ -- Sorta possible but the game doesn't really support it. At least not yet (DLC).
Same goes for crafted pieces. Tier 1 is like intro/beginner, so it becomes outdated fairly quickly unless you're going slow (especially on Nightmare). Tier 2 is like experienced and maybe master, so its useful but after a certain point becomes useless as well. Tier 3 is like master/grandmaster and its what you want for the ending and beyond. There are Tier 4 materials for things but no recipes (yet).
So the game is divided into 3-4 'sections', even with its 'open world' design. You may want to 'complete' a section before moving on with the main story. Hinterlands is obviously going to be more important for the Mage/Templar story, and Western Approach is obviously going to be more important for the Warden story, etc.
This is all going with the assumption that you do eventually want to do ALL content, but just don't want to get annoyed or burned out or confused.
Hinterlands has the most content and feels the biggest, so you won't have nearly as much trouble with several of the others. Fallow Mire was super fast, done within a few hours, entirely.
By being completionist, you WILL overlevel. On easier difficulties, this can kinda suck, since you're finishing combat super fast. On Nightmare or maybe Hard, this can be a boon, letting you enjoy the pace of battle instead of "OH DAMN OH DAMN" and hitting giant HP/Armor sponges for several minutes.
Warden quest is more of a 'NOW the Inquisition is SERIOUS' thing, while Orlais quest is more of a 'Ahahaha, now the Inquisition can have some FUN!', so pace/choice the order of them accordingly. Mage Path has things more dire, while Templar path has things more bizarre, though both have elements of the other. You may want to wait to do Arbor Wilds until you're at least nearly complete with stuff, or you can just push through it, since the Final Boss is one big "POINT OF NO RETURN. WE ARE SERIOUS." sign so there's no issue with screwing up.
Do a run through of talking to companions after every big zone questing trip, or at least a main storyline quest. Check War Table whenever possible.