Upgrading what should go first.

[AztecAsh]

Okay I need some advice. I am currently in a position to upgrade a few components I know my power supply which is pretty old and graphics card has to go and I'm debating between a RX 480, GTX 1060, or a 1070. But what else should I try to invest in. Any advice is greatly appreciated.
Here is my current computer setup:
CPU
Intel Core i5-4670K 3.4GHz Quad-Core Processor

CPU Cooler
Corsair H100i v2 70.7 CFM Liquid CPU Cooler

Motherboard
MSI Z87-GD65 Gaming ATX LGA1150 Motherboard

Memory
G.Skill Ripjaws X Series 16GB DDR3-1600 Memory

Storage
Samsung 840 Series 120GB 2.5" Solid State Drive

Western Digital Caviar Black 1TB 3.5" 7200RPM Internal Hard Drive

Video card
Asus gtx 770 direct cu ii 2g

Case
Fractal design R4

Power Supply
EVGA SuperNOVA NEX 650W 80+ Gold Certified Fully-Modular ATX Power Supply

Monitor
Asus VG248QE 24.0" 144Hz Monitor

Thanks again for any help provided.

 

[Isokolon]

If you didn't run into any troubles concerning your PSU, start with Graphics. For 144hz 24' I'd look around to find a cheap 1070 (doesn't have to be a crazy oc'd model depending on your budget)
And upgrade your RAM, 1600 is a bit slow. But depending on when you plan on upgrade everything else (and to what) you could wait.
The other components should do for now.

 

[NNisar]

You are good to go to graphics card upgrade. If you are gamer then your computer setup looks very great for gaming beside GPU.
You could buy RX 480 in $250 -$300 , GTX 1060 in $300-$350 and GTX 1070 in $400-$450
If you have money or If you are steaming than you could buy GTX 1070. [Else] You need a budget king then you should be buy a RX 480.

On other option GTX 1060 great performer but one tiny problem is no SLI. your motherboard can run multi GPU tech SLI and Crossfire. You probably need to use this feature. It really help with 4k or multi monior setup. your power supply is good to go to multi GPU. don't worry about PSU

Asus VG248QE this kind of monitor can support GSync I am not sure because there two types of model out in market with gsync and without gsync. But checkout that and if it capable of GSync you should go for Geforce GTX 1060 or GTX 1070. GSync really help while gaming while Screen tearing and shuttering

Asus VG248QE is a 1080p resolution monitor then Geforce GTX 1060 is good. [OR] if you have any idea to 4k monitor then you should be buy a GTX 1070.