Connecting with only JTAG
Actually, the best way to learn about a new device is to buy already made board and experiment with various peripherals, one peripheral at a time. Then you can design your own board with only the peripherals you need. Once you have your own board, you can quickly bring it up using the code you have already developed.
To answer your question, most micro-controllers just need to have the clock pins, and power pin connected to bring them up. Just be aware, ARM micro-controllers are quite complex compared to say Atmel AVRs or PICs. Refer to the datasheet for the ARM device you are interested to make sure all power pins are connected properly as there are multiple power pins (Vcc, Vccio, Vccad, etc). Don’t forget about bypass caps and some power pins may require power planes on the board.