Well first off, mixing and matching gear from various vendors will probably lead to headaches and wasted money. If you ordered an iPhone, obviously you will want o pair it with an Apple Watch which was designed specifically to work with.
Is it worth it? For me it is. I like getting notifications on my wrist for my phone without the loud ding. Gentle taps on my wrist lets me know something of interest just came in on my phone. Especially if I'm at the movies or out at dinner. The fitness aspect is very nice and huge for me as well. A lot of good data is captured and in general its a good tool that helps you in getting healthier if you use it as such.
Depending on the version you get and bands, it's appropriate for any occasion.