Actually the trading and such in MGO is pretty easy to deal with. I can remember very, very few times where I couldnt get whatever the heck it was I was looking for.
There exists an extreme number of what I always called "bot shops". Essentially, prices are set for a shop, for every conceivable card (I assume there must be some giant database of doom somewhere that keeps track of this, that all these things must use), and you can go in, browse as you want, and typically find what you want. The costs are generally equal to the card's actual value: If you're looking at a rare card that might be, say, $15 to buy IRL, chances are it's about 15 in there too. Though that's just an arbitrary number I pulled outta who knows where. Very few cards ever go THAT high (that'd have to be REALLY freaking rare), though you likely already have a decent idea as to general pricing and such.
Either you can trade cards directly to it, so long as they add up to the value of whatever you're after (be it a single card, or a bunch that you're after at once), or you can pay with "event passes", which, aside from being used for events/tournaments (duh), are also used as currency, since they cost exactly $1. With many of these things you can also "sell" unwanted cards for event thingies. The things also couldnt care less most of the time if you're trying to trade for some uber-rare card from an alternate reality by throwing a big damn pile of commons and some uncommons at it, so long as it adds up.
So that's basically how that works in that game.... as with any form of trading, it can be time consuming, as chances are during deck building there's multiple things you want, so of course you have to go through your own collection and see what can be parted with, and go look and see how much the thing you want is going for, and so on..... The good thing is that most of the "shops" tend to have 8 quazillion cards, so most things are easy to find.
And, of course, there's normal trading as well, though as always for me I tend to avoid doing that if it's not with friends and such. Some players of course will totally prefer this type, which I can understand. But me, I'm impatient and when I want something, I want it RIGHT THE HECK NOW, so I just use the shop things.
As for MTGO having dull decks to fight.... I've found that's not the case. This isnt Hearthstone, where there's like, TWO damn modes, which is one of my few problems with that. Every conceivable format that has ever existed for Magic matches in general exists in the online version, and i've found that it's usually very easy to find opponents for pretty much everything. As much as I love the game, and TCGs in general, I'm not the super-serious tournament type, or that kind. Alot of THAT, as you know, tends to involve the same decks, often COPIED from someone else, not built, and I haaaaaaaaaate doing that. If I'm gonna have a deck, it'll be MY bloody deck. I get no satisfaction out of a victory otherwise. So I play piles of other modes, whatever the heck I feel like at the time. Some of course are using only the card sets in the current rotations, some may be older sets only, others might be whatever the heck you want.... which is the other thing.... I wouldnt play this version whatsoever if I didn't get to have continuous use of all the cards I already have.
As for dealing with AI, THAT one is up to the player. USUALLY.... not always, but usually.... I get bored of AI in competetive games very fast. Part of this comes from playing too many fighting games, where the AI is weak even at the highest levels. And of course if you've tried Hearthstone at all, well.... then you've seen the lowest level of TCG AI, hah. The AI has to be bloody BRILLIANT, as AIs go, or it's not gonna last long.
....which is another thing about their damn expansion. With AI that blasted weak, why focus on this singleplayer junk? Ugh. I have alot of respect for Blizzard, but I just dont understand them sometimes, I really dont.
