Dragon Age Inquisition is quite parallel to Witcher 3. I'd argue they both suffer from the same flaws but where Witcher 3 delivered more on gameplay, Dragon Age Inquisition delivered more on story. Not really much comparison between Witcher 3 and Mass Effect. Andromeda could take after Dragon Age Inquisition though. We'll have to see.
Keys to Gwent:
-On factions like Monster and Skelligar, you'll want to pile a lot of cards in your deck that are played with another of the same type but only if you have 3 or more cards of that type. At the beginning of the match, if you see any duplicates in your playable hand, swap them first because you only need one to play them all of the same kind.
-On factions like Nilfgard and Northern Realms, the key is decoys and cards that, when spent, give you more cards (costs one card, get two back). If the above rule applies, always play those cards before playing these cards. If you get a card from your deck that matches the type you already had, you just wasted your spy card. Further, I recommend playing these cards first so you can truly see what you have to work with at the start. Additionally, the AI may use a decoy and send the card back to you so you can revive in the next turn with a medic.
-No matter the faction, always take the high value cards that buddy up. Case in point, there's 4 cards of the same type in the Northern Realms hand, each with a value of four. By themselves, they're not very potent but together, they're omnipotent. If you manage to play all four without them getting lost, you'll get 16 per card (4 -> 8 -> 12 -> 16) times 4 for a massive total of 64. Throw a horn on that and that'll jump up to 128 points for 5 cards. There's not much that can beat a hand like that.
-Always play on the offensive. This means take the fraction abilities that boosts rows of cards. This serves as a force multiplier.
-Have at least one commander horn in your deck. They double the value of all the cards in the row that don't have a star around their indicator.
-Medics are crucial to a lot of factions. If you have a medic that is not starred, remember that you can not only revive the medic, but also revive another unit with that medic. One medic could revive many medics and end with a unit card. It's the equivalent of Gwent necromancy.
That said, it's usually best to either revive a really strong unit that will land on an already used horn or a spy to get you two more cards from your deck.
-Special cards generally suck. I only ever take two decoy (to return spies to sender) + one horn. If I take any environmental ones, it would just be a clear sky incase the AI really screwed me over with a torrential rain, blizzard, or fog. Generally speaking, I don't recommend it.
-Beware of scorcher (appears all except early game) and the three unit-killing cards (these are Blood and Wine cards, if memory serves). The best solution for all three types is to always preempt with a high value card. For example, I place my 8-point catapult before the 6-point so if the scorcher is used, it spares all of the 6-point catapults.
-Try to only focus on one row per round. Which you should focus on depends on the cards you have, what your commander can boost (or attack), and which rows have status effects.
-Excepting the spy starred card (very late game) don't play starred cards until the final round. One exception: if the AI capitulates early and one or two starred cards will win the round, go for it. For example, the last game I played the AI passed with only 12 points. I used the Gearlt card (15 points starred) to win the round and that was literally the only card on my side.
-Always try to win the first round. If you do not, the odds of winning plummet. If the AI comes out swinging on the second round, don't be afraid to cut your loses and go to the third (example, you were playing lots of artillery and it throws a torrential rain at you with no way to clear it).
-Don't spam low value cards in your deck. Having high value/tactical cards exactly at the minimum (22 cards) is the best because you're more likely to be able to play the really good cards. For example, a 1:22 chance of getting a spy card is much better than a 1:40 chance.
-Get familiar with attacking. For example, the Monster faction has the 3 crones played to the close combat row that are worth 6 points each. I'll either hold my 7-point close range attack card until the crones are played or have a plan to be able to revive it with a medic should I need to use it. The 18 point crone attack (potentially 36 points if there is a horn) will drop to 0 while I get 7 or 14 points in return. Beware of this vulnerability when playing as Skellegar or Monster factions.
-If you're running away from the AI in points on the second round, it may be best to pass and keep your remaining cards for the third wave. The AI will try it's best to beat you because it is do or die. This should make the third wave easy to win so long as you still have decent cards to play.
-If you're playing as Scoitael, Monsters, or Skellegar, against Northern Realms or Nilfgard, make sure to stock up on decoy cards to turn the spies against them. They'll roll over you if you don't.
I really like Northern Realms and very rarely lose (usually Nilfgard because they out spied me, Scoitael because they played everything in the archer row where I can't hit them, or Monster because I had no way to stop their onslaught of united cards + horn). I have all of the spy (Thaler, Dykstra, that one guy) and medic (Yennifer + generic medic) cards I can get my hands on, lots of artillery (including the two 8-point pairing catapults), pairing archers (5 points each), pairing swordsman (4 points each), and about 5-6 starred 10-15 point cards.
I'm not sure what you mean by only "play with one set." Before the match starts, you can usually change which deck you're using. I'd play with my best.
