Dragon Age Origins: one of best games, epic stories, lots of choices, good romance. Dragon Age II: a filler, bit boring, but worthed Dragon Age Inquisition: you think this is the end? Think again. Recomend to have all DLCs
Uhn... Well, since you didn't play the other DA games, I think you'll be fine... Hopefully... *shivers* I honestly am not in the mood to make a long rant, so I'll try to keep it short... DAI was the worst game ever made by bioware (except maaaaaaaaybe Mass Effect Andromeda), I wouldn't recommend it even to my worst enemy. (not that I have one anyway, but you get the drift) Let me try showing a few downsides of the game. (please take note I only played the game on the hardest difficulty, so parts of this may not apply on lower ones) It's more buggy than Bethesda stuff. Friendly Fire was absolutely horribly implemented. (Chain Lightning has 100% chance of hitting the caster if you turn it on) Tactical Camera doesn't work properly (casting revival spell on it makes it simply... Not be cast, for example, Rogue's parry also doesn't work) Levels matter more than stats (as in, the damage you take/receive is based on the difference between your level and your opponents', instead of depending mainly on stats), which make fights against higher level opponents a huge chore and forces you to grind for the sake of going through the story because you'll be horribly outleveled otherwise. (for the record, you didn't need to grind on any of the other DA games) Very very veeeeeeeeeery short story that is made artificially bigger by forcing you to grind in-between story events. Your character is basically a pokemon that gets a position of power for 0 reason. Heavily conflicting lore if compared to previous games. (shouldn't be a problem if you didn't play them) Invisible walls that force you to go through the annoying confusing path they put to you, even though it's supposed to be an Open World game. (On that matter, it's the worst Open World I have ever seen) Very little build variety. Very little skills available. Very small skill trees. (yes, it is different from the previous point, passives are also included on skill trees) Most choices given to you make little to no impact on the overall outcome. (they need your choices to matter little because they'll make a sequel afterwards, so it's understandable... Still annoying though) Your character's race/gender makes very little difference to how other characters treat you, which is absolutely immersion breaking when you consider how other characters of other races face heavy racism on the other games. Even though you get a position of power, 99% of the work you do is groundwork that should be done by literally everyone else aside from you. (more immersion breaking here) Mechanics that force you to wait RL time to get things done, which are just another way of artificially increasing your playtime. Loading times as bad as Sonic 2006 ones (at least on the PS3, I don't know how bad it is on other platforms) Very very poor animation quality (you can see a knight's shield piercing his own shoulder on the title screen, literally the first thing you should see on the game) Fights that reset for no reason if you try to go away from the terrible positioning they put you in and try to kite enemies to a place in which you have the advantage. Almost unreadable map. (This might not be a problem for most, but I'm absolutely terrible with directions, so I got really annoyed when the first 2 games had excellent maps and this one had a horrible map and the most confusing layout due to the poorly implemented Open World) Horrible Villain and very non-engaging (boring) storyline. Almost anything you do will basically never be brought up again on future games, your character will never appear again and the very few things that appear as a cameo won't have any significance, which can be a huge turn down if you're looking forward for future games of the series. (I kinda talked a bit about it above, but figured I would be more clear about it) That's about as much as I can remember without going on a full-blown rant about how much I hated the game. I heavily recommend not playing it. (for the record, the 1st game is amazing and the 2nd game is okayish (if you look for public opinion, you'll see that the 2nd game is the most hated of them all, for me, it's 10x better than the 3rd game, and I don't like the 2nd one), so I would recommend just buying the 1st game of the series instead.) If anything, I suppose the characters (except for you, you're a pokemon) of DAI are pretty good, and pretty interesting overall... They don't make the game worth it by themselves though. Darkest Dungeon on the other hand is a game I didn't play, but heard lots of praises about, so I would recommend it easily instead. They are different genres though, so it's hard to make a proper comparison.
For DA you should go straight to the first one - Origins - and ignore everything else. Darkest Dungeons... haven't play that one though.