I'm assuming you actually mean you want to get some practice in on the idea of designing a micro of some kind. You are in huge luck. I had 7400 series parts to work with and wire wrap and tons of money that had to be spent that I didn't have. You get FPGAs for nearly free, free software tools that include VHDL and Verilog, automated floorplanning, downloading and testing. I am so envious of what is available today. (I've designed processors before.)
If you want a really good overview book that gets into enough detail to get you really thinking, without being cryptic and overly pedantic, I highly recommend "Bebop BYTES Back: An Unconventional Guide to Computers." I have several copies of it and sometimes give it out to interested parties. It's pretty good. There are also some simulators, as well, that do an excellent job and don't cost a penny and let you try out schematics you write up. They will include display modules and keyboard modules, so you don't have to work hard for those parts. Finally, and it's getting to be a little older but still unique in the way it handles teaching both VHDL and Verilog at the same time, is Smith's "Hdl Chip Design: A Practical Guide for Designing, Synthesizing & Simulating Asics & Fpgas Using Vhdl or Verilog" It really can be read by someone new and used for very practical learning.
As far as the easier processors, I'd have to say that the PIC12 family is probably the most bare bones of anything. Looking at the instruction set, you can almost "see" the explicit logic blocks in plain view. Nothing fancy, it's just an exposed ALU with almost nothing extra to it. You'd almost imagine designing it in a day or so, if you had to.
Of course, none of this deals with peripherals. They can be quite complex, actually. So that's another deal to dive into, after you've got a flavor for the basic ALU, register file, program counter, and latches and buffers and internal buses worked through. The Bebop book will give you a huge leg-up there, too.