Here is a build i have put together for you.

For the OS the cheaper option is to go to microsoft website and download the OS and put it onto a USB stick. Buy the Retail product key on a site like g2a and enter it when your loading up the OS from the USB on the new pc. Otherwise a windows 10 from pcpartpicker and nearly all websites will set u back around $100 whereas doing it the way i said above will set u back around $25
The SSD will be used for the OS and his 1-3 main games. The WD Blue HDD are pretty fast and will be able to hold all his other games and files easily.
The 1070 is one of the best 1070's you can possibly get atm its a excellent bit of gear imo.
The case is pretty premium aswell and has nice cable management and ofc a nice side window.

PCPartPicker part list: [ Register or Signin to view external links. ]
Price breakdown by merchant: [ Register or Signin to view external links. ]

CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor ($328.99 @ SuperBiiz)
CPU Cooler: CRYORIG H7 49.0 CFM CPU Cooler ($29.90 @ Newegg)
Motherboard: ASRock Z170 Pro4S ATX LGA1151 Motherboard ($72.98 @ Newegg)
Memory: Avexir Core Series 16GB (2 x 8GB) DDR4-2400 Memory ($67.99 @ Newegg)
Storage: A-Data Premier SP550 120GB 2.5" Solid State Drive ($42.98 @ Amazon)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($48.89 @ OutletPC)
Video Card: EVGA GeForce GTX 1070 8GB SC Gaming ACX 3.0 Video Card ($389.99 @ Newegg)
Case: Corsair 450D ATX Mid Tower Case ($98.00 @ Newegg)
Power Supply: EVGA 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($116.89 @ OutletPC)
Total: $1196.61
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-11-13 16:56 EST-0500

Kind regards

ELACTIX wrote Here is a build i have put together for you.

For the OS the cheaper option is to go to microsoft website and download the OS and put it onto a USB stick. Buy the Retail product key on a site like g2a and enter it when your loading up the OS from the USB on the new pc. Otherwise a windows 10 from pcpartpicker and nearly all websites will set u back around $100 whereas doing it the way i said above will set u back around $25
The SSD will be used for the OS and his 1-3 main games. The WD Blue HDD are pretty fast and will be able to hold all his other games and files easily.
The 1070 is one of the best 1070's you can possibly get atm its a excellent bit of gear imo.
The case is pretty premium aswell and has nice cable management and ofc a nice side window.

PCPartPicker part list: [ Register or Signin to view external links. ]
Price breakdown by merchant: [ Register or Signin to view external links. ]

CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor ($328.99 @ SuperBiiz)
CPU Cooler: CRYORIG H7 49.0 CFM CPU Cooler ($29.90 @ Newegg)
Motherboard: ASRock Z170 Pro4S ATX LGA1151 Motherboard ($72.98 @ Newegg)
Memory: Avexir Core Series 16GB (2 x 8GB) DDR4-2400 Memory ($67.99 @ Newegg)
Storage: A-Data Premier SP550 120GB 2.5" Solid State Drive ($42.98 @ Amazon)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($48.89 @ OutletPC)
Video Card: EVGA GeForce GTX 1070 8GB SC Gaming ACX 3.0 Video Card ($389.99 @ Newegg)
Case: Corsair 450D ATX Mid Tower Case ($98.00 @ Newegg)
Power Supply: EVGA 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($116.89 @ OutletPC)
Total: $1196.61
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-11-13 16:56 EST-0500

Kind regards

120GB SSD in a $1200 build? Wat?
No need for 850w. A good quality 650w unit shall suffice.
The 1070 is not "the best 1070 atm".
Not the best way to spend $1200 imo.

ELACTIX wrote The SSD will be used for the OS and his 1-3 main games. The WD Blue HDD are pretty fast and will be able to hold all his other games and files easily.

120GB SSD in a $1200 system is pitiful. Also, paying $50 for a 1TB HDD doesn't really make sense when you can get an HDD twice the capacity for the same price.

ELACTIX wrote The 1070 is one of the best 1070's you can possibly get atm its a excellent bit of gear imo.

Source?

ELACTIX wrote The case is pretty premium aswell and has nice cable management and ofc a nice side window.

Over priced though. There are better options at better prices.


OP- assuming all peripherals are decent, I'd get something like this;
[ Register or Signin to view external links. ] / [ Register or Signin to view external links. ]

CPU: [ Register or Signin to view external links. ] ($235.89 @ OutletPC)
CPU Cooler: [ Register or Signin to view external links. ] ($29.90 @ Newegg)
Motherboard: [ Register or Signin to view external links. ] ($124.99 @ B&H)
Memory: [ Register or Signin to view external links. ] ($81.89 @ OutletPC)
Storage: [ Register or Signin to view external links. ] ($136.99 @ Newegg)
Storage: [ Register or Signin to view external links. ] ($49.50 @ Amazon)
Video Card: [ Register or Signin to view external links. ] ($393.99 @ SuperBiiz)
Case: [ Register or Signin to view external links. ] ($109.99 @ Newegg)
Power Supply: [ Register or Signin to view external links. ] ($86.99 @ NCIX US)
Total: $1250.13

You don't really need the HDD right now, the SSD would be more than enough, so I would drop the HDD to get the system within the $1200 budget, and you can add the HDD later if necessary.

Here's what i put together

[ Register or Signin to view external links. ]