Arena Handbook 2nd edition with an alternative FAQ for MTGA
Classic Karsten’s guide to manabase updated for the recent sets
Classic "What I know about Magic" guide to deckbuilding, archetypes and types of players.
A reddit thread summarizing the numerous guides from Wizards of the Coast and Star City Games
Building better decks guide by metamorph
A guide on sideboards from the sub (to be reviewed later)
MTG storyline condensed by Vermilious if you want to blaze through the lore
There's no centralised place to discuss the tournaments in Magic Arena yet, so the next section covers what we have so far