What social media platforms are worth spending your time on?

As someone new to business and marketing and all of that fun stuff, I am finding myself getting overwhelmed with all of the options that are out there! Do I use Facebook? Do I use Instagram? Do I use Snapchat? Do I use Twitter? Do I use LinkedIn? Do I use Youtube? Do I use Musical.ly? Do I use them all?!

I'm trying to build my social network and really take advantage of the online resources available to me to help grow my brand and improve my connections to the industry. Each platform appeals to me in some way, and so I guess I'm looking for some advice on how to pare down my options and hone in on the social networking platforms that are actually worth having time spent on them.

Facebook is interesting because it's one of the most well-established social networking platforms. But I'm worried it's a little too behind the times - is business promotion only useful on Facebook when your business is solely targeted toward a small geographical community?
Instagram is neat because of the way in which you can represent your brand through imagery. It's easily digestible and can really add to the aesthetic of your product. However, it's limiting in how you can provide information to prospective customers. Nobody wants to read long captions or see weird long links to other sites in the description.

Twitter is very immediate and to the point. You can link things effectively through twitter and the re-tweet function is really key, I think! But I worry about it falling behind in some ways like Facebook. Is it really still so relevant? And again, how likely are people to want to access information about my product beyond the limited, bite-sized snippets on Twitter?
Now, Snapchat and Youtube are video platforms, and by most people's standards might seem to be a pretty big waste of time for businesses to get involved with. But what about brands and branding deals? I don't think our product or company would ever be in front of the camera with its own channel and everything, but couldwe not look in to getting well-known Youtubers or Snapchatters to endorse our product/brand? How would we go about doing that? Does it even reap that many benefits? How much do you have to pay the individuals?
Lastly (because Musical.ly was a joke), LinkedIn seems like an obvious yes to me. It's one of the more professional, polished, and well-received social networking for professionals platform out there. It's something that I know a lot of employers and head hunters rely on. Is it something you think a investor would want to look at? And is it actually valuable beyond proving your professionalism and keeping an address book? How often do you think the posts of individuals and the forums and such as looked at?
Maybe I need to combine a couple of platforms to get everything that we want out of a social networking experience? Sorry if this is long-winded or seems super obvious. It's just that time is money, you know, and I want to get our name and brand out there, but in the most efficient and effective way possible.