Facebook: Having gone to school in Boston, my college was one of the first 10-15 to join the website, having to actually petition to get our school's .edu added to the servers so we could even create an account. It was cool and exclusive at the time, and I remember watching a lot of my high school friends pop up as their colleges got added to the list. When it opened to anyone (high school / adults), it exploded in a lot of ways I wasn't happy with. Over time the content of my peers changed - posts and pictures of bikinis and drinking turned into pictures of weddings and babies. Nothing wrong with that, mind you, but it became more about "staying in touch" with life events than seeing what people were up to immediately. Since then, it has become a landfill for who can share the stupidest video they've seen that day, and even after trimming my friends list down, I can scroll for 20 minutes and get roughly 2 posts I'm remotely interested in. It has become a bigger waste of time attempting to scroll through my feed than actually contacting someone, not to mention the ads.
Two ways I still use it that its great for:
1) A lot of courses have a FB page and they will post upcoming tourney info, league results, etc. I've attended tourney's that I only ever heard about through FB.
2) Since almost everyone I know is on FB - the "Events" section gets used a lot. Having a Halloween party? Bday party? etc.? Create an event and invite everyone via FB. My sister didn't get invited to our sister-in-law's bday party recently because she doesn't have FB anymore and nobody remembered that fact and forgot to invite her via text/call. That was very funny to me.
Instagram: For following people and tours. My feed is 90% disc golf. Follow all the pros, follow all the tours, and see clips and posts about every major event out there. It does somewhat kill the excitement of watching the post produced stuff when you've watched clips of 6/10 of the shots already on your phone and know the scores, but I know what I'm doing when I watch them. Otherwise, follow other famous people. Comedians are funny, politicians are a joke (not in a good way), follow Dwayne Johnson or some other fit-person if you want gym motivation, etc. etc.
Twitter: Well, its not censored, so be careful what you get into. There are too many hashtags you can take advantage of to completely avoid this app, coupons/deals, etc. A major convention I enjoy going to posts when their tickets go on sale via their twitter feed, and sells out within hours, so getting that notification is important to me. Otherwise most things on Twitter can also be found on Instagram. I really only open this app if I'm really bored / have already caught up on Instagram, or have already gotten frustrated with FB. This is all assuming there's even time for that (yay for bathroom breaks!).