As my Home Page suggested, I've got a lot of experience building custom desktop computers- many of which I probably should've gotten pictures of. That being said, here are some of the computers that I've planned and built ground up myself (with my dad's supervision in 2019 being an exception). I've built a few more outside of these that I did not document so well, however as I continue to build I will hopefully get more professional level pictures to showcase here or wherever I decide is worth showcasing them.
I typically use either Microsoft Excel to plan parts and budgets, or just the classic PCPartPicker.
My first real hands-on hardware experience(s) are from back when I had my first PC, a Dell Optiplex 780. It came with a Core 2 Duo E8400, 8gb of DDR3 1666mhz memory, and some mechanical hard drive. My first efforts towards making the system more suitable for my needs/wants as a kid involved buying more dedicated memory, and swapping in a Core 2 Quad Q6600 (equal in most performance to the E8400, while somehow sporting more cores and threads. Was good for my primitive Blender rendering days using Blender version 2.6).
From then on out, I just kept learning and working on computer hardware. It's something I have always found to be really fun, and I'm very glad that I started in the first place.