Just a bog standard iPhone 5s. I tend to take multiple versions of the same shot, and make sure to tap the screen on the focus/exposure point of the photo.
I also use an app called Colour Story to tweak the colours and exposure a little. It’s way more subtle and flexible than the filters on Instagram. The only thing I do in Instagram is to slightly increase the contrast.
For example here is the original picture through the train window:
Here it is after a little tweaking on Colour Story. I mostly use the Good Vibes and Chroma sets of filters at a low %.
And here it is after a slight tweak of +20 contrast on Instagram.
I end up with three copies of the same pic in various stages, and I just go through and delete them every now and then to save space.