Good stuff here. I'm not a video game guy, but FIFA has introduced the game to a lot of people. Kind of a weird time to start following a team, but there will be pre-season type games coming soon.
Don't think you're likely to be a hard core type guy so I'd keep the team picking simple. There are lots of good reasons to pick any of the bigger teams, but I would steer you to one of the bigger EPL clubs. WGAF if anyone considers it bandwagonning. Easiest team right now for an American would be Chelsea with Pulisic(of course that could change lol) and new American owners vs. their Russian oligarch.
The leagues/cups are kind of hard to explain unless you follow when they're going on imo.
Everyone will tell you their team is best to follow and that the other fanbases are aggy/ou/Tech fans. It's all crap, just depends on your perspective fr the most art. While I say to not over think your club, you may want to look at the club a little bit. Many have strong ties to the communities/origins. If you are a hard core conservative, you may find following Liverpool or everton a little hard. If you dislike certain religions/denominations following Spurs or Celtic or Rangers might be a little weird.