Low-Light Photography?

I use a Nikon D5200
-Nikkor 50mm f1.8
-Nikkor 55-200mm f4-5.6 AF/VR
-Nikkor 18-55mm f3.5-4.6 AF/VR

In addition I use a tripod.

I am alright/good with taking pictures with sufficient light, but, who isn't…

I suck terribly with low-light - too much noise (too high ISO), or, when I'm taking pictures of lit object surrounded by darkness, for example, the skyline of my city at night - the lights will either be vastly over exposed or the darkness will be disgustingly noisy/orangish-brown (though that may just be light pollution)

What are some tips/tricks - things to read?
In reality, how do I find a balance between shutter time and ISO - and should I buy a flash/reflectors?

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