Facebook to find your local scene, since some share their tournaments, carpools, Wis-Fi matches and more there. Also, there is Discord, where you can join character servers and servers based on your region, since Smash 4 players tend talk there moreso than there ever since Discord came to be. The character servers here are rarely active due to that.
Link:
https://smashcords.com/smash-4/
In the character servers you will find resources for your main, players posting tourney VODS while getting feedback, general competitive talk where players can ask questions and get advice or talk about their character's options, the general chat, memes, and more things that change depending on the character server you are in. The servers also have JMU's (joint match-up discussions). There, 2 character servers discuss a match-up for a week, and then players are selected at the end of the week for an online crew battle that is usually streamed and sometimes archived on youtube. They also watch tournaments and cheer on players who play their character.
As for meeting new people, going to your local tournaments, regionals, smashfests (evening or night of casual/competiive smash, a.k.a training), and arcadians (tournies where the PR players are not allowed to give other players a chance) are where you want to be if possible. If you cannot attend those, then online matches on Discord or smashladder.com (slightly better For Glory in my experience) are options you have for improving.
