I have been Zbrushing for about half a year on a laptop of mine. I tend to make a lot of creatures and monsters and I am about to start classes at SCAD to study game design and I decided I wanted to build a computer specifically for these programs. I have had issues with lag and delayed brush strokes once I hit around 3 million polygons on a sub-tool or have a million or so on a few sub-tools. It is not my RAM because I have 8GB of RAM and I am aware Zbrush can only access 4. I was just wondering if you kind people would have any suggestions on computer parts because I am going to be building one with a friend. I have a budget of 900-1000$ but I cannot go over that because like I said I am a student and money is hard to come by. If you guys could help me decide what I need that would be fantastic!
-Thanks! 
Well a budget without any other information doesn’t really help that much, so I’ll ask.
Do you need monitor(s), a new mobo, gpu, cpu, hdd, or ssd, keyboard, mouse, tablet, an OS, PS. Basically, are you building from scratch or upgrading?
I will be building it from scratch but I do not need a tablet, mouse, or monitor. Everything else will be built from scratch
What other software will you be using besides Zbrush?
I will be using Zbrush, Maya, and the rendering program Keyshot for all of my sculpting. I also paint some over my sculpts in Photoshop but I have never had any problems with it.
https://www.motherboardsdirect.com/index.php?main_page=product_info&cPath=117_120&products_id=547&zenid=ce3616c0f68a782f76a05cc584ffdfec
Only 4 GB Ram though. ~$350
Some people recommended an i7 processor is that something that is very important or does it just help certain things out