well you want the flipper and the wifi dev board at the very least.
gets you to doing fun wifi things. Flipper itself has no wifi frequency capable hardware.
I ordered the GPIO pin headers for doing hardware things, but honestly I probably won't use them and neither will you unless you're looking to jtag shit and download bins and what not.
so if I were ordering one brandy new right now I'd:
flipper
case
screen protector
wifi dev board
and be done.
then just hit up the github, slam the unleashed or rogue master firmwares on it. You need a micro SD card, does not come with. I stuffed a random 32GB one I had in him. then the rest of it is just downloading files and sticking them on the SD card for the apps to use.