Building a PC is very easy, but if you do a basic build at Microcenter (if one is near you) the will only charge $99.00 to put it together.
Here are my tips:
1. Determine your budget
2. Do your research AMD/INTEL etc. right now you can get current generation cheap because new CPU/GPUs are
just a month or two from release
3.
https://pcpartpicker.com/ is your best friend for determining where to order (get cpu/mobo from Microcenter)
4. If you buy the OS, buy OEM version, or if you want to live dangerously, you can get it cheap from CDKeys.com etc. but do so at your own risk
If you have a build in mind and have questions, post it here, happy to help you out. I have built about 20 PCs for myself and friends and have been doing it since 2004. While I won't build it for you happy to share my advice.