As already noted, the W65C02 uses an 8-bit parallel data bus and a 16-bit address bus, so 64KB (65,536 bytes) is the native range and I/O also needs to be mapped as part of that space.
With the current pricing of SRAM and EEPROM, I'd suggest you just pick up a 32KB SRAM (Alliance AS6C62256-55PCN) and a 32KB EEPROM (Atmel 28C256) , plus a few logic chips, like a 74HC00, 74HC30 and 74HC138, along with a clock oscillator, a DS1813 reset chip and some caps, switches, sockets, etc. And of course some sort of I/O device so you can talk to it (UART is fine, but be careful using the W65C51 as the latest WDC part has problems).
This will allow you to build something reasonable and simple up front that you can actually work with. In addition to Garth's primer (should be considered required reading), I'd also suggest looking at Daryl Rictor's older SBC 2.5 shown here:
http://sbc.rictor.org/sch2.htmlThis will give you a more flexible system once you breadboard something from Garth's primer. Finally, you might find Ben Eater's recent 6502 video interesting:
https://eater.net/6502 Good luck on your new venture