You probably won’t get much help for Smash here. You might have to check out reddit or SmashBoards for that. For SFV, there is a forums here for that, but there are also loads of guides and videos on youtube. Gief’s Gym is a pretty popular book for new players in SFV, and VesperArcade has a lot of good videos on youtube. Jmcrofts is another good youtube channel. You can also seek out your local FGC and see if there is a scene. Just google that or check out the regional matchmaking forum here. If there is a scene, more than likely they have a facebook page.
As far as gear goes, a PS4 controller is just fine for SFV. A lot of pros use it. If you get an arcade stick, I recommend getting one with Sanwa or Hori Hayabusa parts. If you cheap out on a stick, you’ll just be stuck dealing with upgrading later on. Madcatz just filed for bankruptcy, so maybe they will be clearancing out some sticks or something. They are alright, but I don’t use them because I just prefer Hori sticks. Also, if you play online, try to use a hard wired connection. It’s just better for fighters than wifi.
Here is a link to some fighting game terms. Just bookmark it so you have it. Smash probably has its own terminology, so bare that in mind.