What I would focus on:
-New 1920×1080, less than 5ms respons time, 120 or 144hz and 24″ or 27″
Switching from 60hz to 144hz is the best upgrade I’ve ever done. It’ll make FPS games such a joy 😀
-New SSD 250gb or more
This will make you save time and I mean A LOT of time. As Tiger says cuts the loading times in half in most games and your pc overall will be more responsive.
I bought a 250gb ssd to begin with but it wasn’t really enough for me. You could buy a HDD to store all your other files. Just a 3.5″ 500gb or 1tb HDD at 7200rpm (anything less than 7200 is painfully slow)
-New GPU: nVidia GTX 1060 or a RX 480
I would go for the mid to low end GPU since you’re playing in 1080p and your CPU is probably not fast enough to keep up with a 1070 or higher.
And yes the the RX 480 is consuming little power but it’s also throttling and can’t even maintain stock clocks because of the low power target. If you decides to get it then go for an after marked cooled version. The reference cooler is very bad at cooling and also loud. The great thing I can say about the 480 is the good support for DX12/async compute and the low price OFC 😛
BTW talking about RAM. I would not get more than 8gb as it’s not really worth it in games. Just get 8gb, 1600Mhz or higher and go for a low CL number. I have tested with 16gb ram myself and it made little to no impact on my fps in games. See for yourself: http://www.techspot.com/article/1043-8gb-vs-16gb-ram/page3.html