I’m looking to start making my own string but don’t know how to do it or what I need to do it. Note I’m not looking to sell but really just for my own personal use. I would appreciate anything from what materials to use, where to buy them, and any tips y’all have. I also want to make them high quality so that I may sell them if I ever decide to do so.
As an experienced string maker -
The best place to get (most) materials is wawak.com. They have unbelievably low prices (a third of what my local sewing store offers), incredible customer service and incredibly fast shipping. I simply cannot recommend them highly enough.
Best material I can recommend is Maxilock thread. http://www.wawak.com/products/category.cfm/cid/1326/Maxi-Lock-Thread/
It’s the same stuff I use to make the strings I compete with (with a little extra added - but I won’t tell what that is 
)
It’s extremely cheap at about $.04 per string, very soft, and plays very, very well, if you can make the string correctly. It does tend to be a little finicky though… a small change in the production process can make the world of difference between a good string and a bad string. Make sure to fiddle around with your setup to see what works best.
There are plenty of guides floating around the internet. This is the one I started with http://www.instructables.com/id/How-To-Make-Yo-Yo-String/
Here is my guide for improving string rig efficiency, if you’re into that kind of thing. Also it gives some tips on how to make string making easier. Making Your String Rig More Effecient - Tips and Tricks - Yo-Yo Mods and Maintenance - YoYoExpert