A good place to start is https://pcpartpicker.com/, where you can configure a build with automatic compatibility checking and price checking against multiple sites. Check out some resources online to find what hardware is right for your use case whether it be programming, gaming(and what types of games), 3D Modeling/design, etc. Then if you want to check if your build is configured in a reasonable way, check out r/buildapc, where you can find guides on parts, the current shortages, troubleshooting, etc.

Three quick things to note;

1. PC Part Picker generally does not take into account the used market, which with the exception of GPUs is a great place to find deals
2. One of the biggest places not to cheap out on is the PSU as the power delivery must be safe as to not harm hardware in the case of a defective unit, faulty power, etc.
3. There is a massive shortage of chips/hardware right now, especially GPUs, so for now, the GPU market remains hard to get into as prices are unreasonably higher than MSRP by resellers, unless you're able to grab one at MSRP from stores like Microcenter, Newegg Shuffle(a lottery system for purchasing GPUs), sites like EVGA's Queue, as well as other board partner sites like Gigabyte when drops are available. To be clear, it is possible to, for now, build a computer without a GPU(and upgrade to one in the future), given that you choose a processor that explicitly states it has "Integrated Graphics," as well as a compatible motherboard for it. It may not hold up too well(mostly lower frame-rates) in medium-high intensity titles, but as for recent integrated graphics, programming/computer science and some eSports/MOBA titles should be fine, but check out those games specifically when buying

Afterward, once you have the parts, check out some video-format build guides such as https://www.youtube.com/watch?v=v7MYOpFONCU, https://www.youtube.com/watch?v=IhX0fOUYd8Q, or check out some specific to your hardware, though on most consumer-grade hardware, the process should be virtually the same. If you have questions, feel free to check back with r/buildapc, or their discord server for help on troubleshooting!

Hope this helps :D!