I've played both Hobbit sagas. Very enjoyable. I have one core, 5 Mirkwood packs. And I have player cards from heir of Numenor.

So I ordered all the LoTR sagas.

Guess I have two questions. Do I have a deep enough card pool to play through the whole thing?

Second question, if all sagas aren't available, I guess you need to play them in order or not at all?

I don't think I'd like to play the last two boxes with that card pool, they are rather difficult. The earlier boxes should be winnable but might take quite a few attempts per quest. You can play individual quests in the sagas without playing the previous ones, just like a normal quest, but you won't be able to play them in Campaign Mode. Campaign Mode is fun, but it's not a huge change to the game, so you can still get most of the fun out of the boxes even if there's one missing.

If memory serves the dwarrowdelf cycle had some excellent player cards and I recommend to pick them up (most quests are fun, too!) regardless.

As NathanH said, the first two boxes are 100% doable, one or two quests might take a while though. Second and fourth box depend on your skill I would say. If you bring good decks and play well it should be doable, but I only played those with a full cardpool.

Last two boxes have some of the hardest quests of the game, so good luck.

Some people like to play quests in a minimal purchase mode (e.g. Seastan, check out his youtube if you like), meaning they only use the cards from one core and the necessary expansions to play a specific quest (=box + AP;/only the box for sagas). I don't know exactly which quests he did so far, but think some were quite tuff. That's just ment as a reminder, that most quests can be brought down with enough tries, regardless of your cardpool's size.

Thank you for the insights, I have to wait and see what comes in.

but I guess best bet to progress with other expansions a bit first.

Don't forget you can play the quests on easy mode. Easy doesn't really mean "easy", they're still tough, but more manageable for smaller card pools.