A good place to start would be reference schematics from Espressif for their dev boards, and schematics from open ESP32-based boards from other vendors. Check out esp32.com for a list of boards.

With those schematics and KiCAD, you should be pretty much set. Take an hour or so watching KiCAD tutorials, it'll be worth it.

Also, spring for an ESP32-WROVER-KIT and use it to prototype with a dev board. That kit also supports JTAG debugging, which can be quite handy.