So, what things must I know about Fire Emblem: Three Houses before I play? I know about the Sword/Axe/Lance triangle and I've played Awakening, but things might be different enough that that's a detriment. If linking vids, please do your best to link one's with minimal spoilers.
You shouldn't need to know anything mechanically, Three Houses isn't terribly hard, even on Hard. Definitely don't play on Maddening though, if that is even available before you beat the game once.
You don't need to worry about the weapon triangle either. It doesn't really matter unless you're playing on Maddening.
If I had some advice, I would not suggest attempting to recruit every character on your first playthrough. You can, and it isn't a wrong choice, but I think you'll appreciate the story more if you don't.
That isn't to say don't recruit anyone from outside your house, but I recommend sticking mostly to the characters in your chosen House, if only so that you don't feel overwhelmed by endless Support conversations between missions. Recruit someone if they seem interesting, but you'll get a better sense of who that character is by playing the route they belong in.
In that vein, just pick whichever House seems most interesting to you, but keep an open mind about things. Which route you play first can definitely color your perceptions.
Azure Moon (Blue Lions/Dimitri) is the strongest story route in my opinion, with its characters having deeply personal and interwoven conflicts, but offers the least insight into the world and the broader conflicts in play.
Verdant Wind (Golden Deer/Claude) is the most classically 'Fire Emblem' story route, and offers a lot of insight into the world, but its characters are the least personally invested in the story.
Crimson Flower/Silver Snow (Black Eagles/Edelgard) has a route split in it. At some point you will receive a prompt telling you that a decision you can make will have serious consequences when talking to Edelgard. In order to unlock the route split you
must agree in this dialogue. This doesn't lock you onto the alternate route, only opens up the possibility later. If you fail to do so, you will be forced onto the 'intended' route (Silver Snow) at the point where you would otherwise have the option to choose.
Silver Snow is quite similar to Verdant Wind in terms of insight into the world, but on a character level it is the most lacking. I'd say that this is the most skippable route.
Crimson Flower (the alternate route) is my personal favorite, but it is also the shortest route in the game, to its detriment. Anything else I could say would be pretty spoilery.
Just have fun. Three Houses is just great.
