Ok so I got my windows 10 from the Microsoft website. They give it free without the key but you will need one. Make a bootable usb drive, Microsoft will do it when you download the installer. I got my key for $20 and its legit.
Aside from that this is your best friend. I was nervous with mine but I read the hell outta the manual. Got it right the first time around. I also made sure that was the first few things I did when I put my mobo in my case.
Chapter 1 page 27
ASUS X99A2.pdf
Imo just get a small sized SSD dedicated to your OS and get like a Western Digital Black in 1TB and up range. Videos are going to take up space fast, especially if you render in HD quality.
I would highly recommend just upgrading. Yeah PS4 has great games out and upcoming (Horizon Zero Dawn....) but honestly its not worth the monthly subscription. So IMO just go for the 1050ti or 1060. Overall its a better experience.