Ben Eater's breadboard CPU is a good way to learn the basics, but since the focus is pedagogical, it's very underpowered for the quantity of chips it uses (and you better enjoy forming wires). For a much more powerful computer built around the same number of TTL chips, see the Gigatron.
Sadly, Marcel van Kervinck (one of the two creators of the Gigatron) passed away in 2020. You can still buy PCBs on Tindie, and the parts are easy to procure, it's all standard 74HCT chips. You can find a detailed bill of materials on gigatron.io, and the PCB files are there as well.
