You can play the game without joining clans, but it's better to join them, even if you don't play too much. Clan members get some benefits from high level activities done by other clan members. I'd recommend that you join a GAF clan.
There is NO matchmaking for raids, but guided games should be going live soon, which is basically, some people in a clan guiding newbies through a raid.
Story is the best it has ever been, even though it falls apart a little, towards the end. The humour is basically a love it or hate it kinda cringey shit, but I mostly like it coz I've got a questionable sense of humour. You don't need to read the summary of the first game but if you did you'd understand the references better. It's not absolutely necessary, but knowing what happened at least till The Taken King expansion will make the new story a bit more enjoyable, imo.
Farming has pretty much been stripped down in this game. If you like the game and play it enough then you'll be getting most things you need at a pretty good clip. Once you reach the end-game, you basically do 4 high-level activities, once per week per character and get rewarded with powerful gear.