Other misc thoughts:
Don't try to save a few dollars getting a cheap, low-quality PSU.
One upside of PCs is modularity. If you're on a limited budget, one option is to select parts where you plan to upgrade and replace components in a year or three. You could start with a CPU with integrated graphics (e.g. AMD-Ryzen-5600G) with the option of replacing that with a better CPU and a dedicated GPU in future -- but for this possible future upgrade path to work you'd need to pick a motherboard and power supply that would support the future upgrade: CPU socket, size & version of PCIE socket, PSU with enough power to support future CPU + GPU -- otherwise upgrading will require also purchasing a new motherboard and going through a complete disassembly & reassembly.
If you're trying to get RAM running at a high clock speed, you need to find RAM sticks that are mutually compatible, and compatible with your motherboard. Mixing sets of RAM sticks from different manufacturers that are all rated at some high clock speed X probably won't work, and you'll get a system that doesn't boot and only communicates the symptom with pc speaker beeps and blinkenlights. This is more an issue when upgrading and adding RAM to an existing system than when starting with a new system. There are some resources online to help with this, if you search for "RAM <brand> compatibility database" etc you may be able to find lists from manufacturers of RAM with RAM+motherboard combinations they have tested and confirm work.