When I am going to build a PC, I buy my computer parts around black Friday - Cyber Monday period because you can get some really good discounts. I mainly shop on eBay, Amazon and Newegg for the parts. Youtube was how I learned to build my first PC and yes there is a wealth of videos teaching you how to build your first PC. Websites like PCpartspicker can also help you work out a build for your budget. What I would suggest doing is once you have chosen a build from pcpartspicker or similar websites is to sign up to websites like Price.com to always be alerted to a very good discount on said components online.