Build a computer from scratch

My name is Matt and I am 12 years old, and am a little bit of a computer geek. My dad teaches at a place called Techshop, so sometimes I get to go there and make things and work on different equipment like 3D printers, which is amazing! I then got really inspired to do my own BIG project - now I am looking to build my own desktop computer by myself. I have saved $42 already but I need a lot more so I'm looking for a job (I did the math and it would take me more than 3 years to save the money from my allowance). Then my mom told me about this website, so I thought I would try to raise some money. I really want to build a computer myself. If I did, I would be able to learn the parts to a computer, how to manage an operating system, and I also think it would be incredibly fun. When I get into high school I can take robotics, but this will give me a head start. Thanks for any donations you can give, I really appreciate it. (PS - I only have Instagram. My  parents don't want me to have a Facebook page yet so this is attached to my mom's).