I'm considering on purchasing a wireless keyboard for my 2012 MacMini. What do ya'll recommend? And also MAYBE a wireless mouse.
Keyboards and mice are very subjective (apparently, some people actually
like the Magic Mouse...), so there's really no substitute for finding a store with a range of them on display and getting your hands on. Do you want low-profile or full-travel mechanical? Numeric keypad? Ergonomic? Mouse-wise, do you want chunky ergonomic or low-profile? Do you use your left hand for the mouse (if so, scrub the MX Master)?
Personally, my absolute favourite is the (discontinued) previous generation Apple
wired aluminium keyboard with numeric pad - the first and last decent keyboard made by Apple this century. If you've already got one of those, or manage to find one for sale at a sensible price, my advice would be to stop worrying and learn to love the wire (plus, it gives you a couple of desktop USB ports, perfect to plug in a Flash stick or hide away a typical wireless mouse dongle).
The new, Wireless Magic Keyboard is OK - they've made the key travel shorter but its still a scissor mechanism, not the dreaded MBP butterfly dust-magnet, but I prefer the feel of the old-style. Also, the new one feels really flimsy (and with feet at the corners only, bends in the middle to touch the desk - not a practical problem but, well, ugh!) - but anyway, I'm not sure if your 2012 Mini has the right flavour of bluetooth to support it.
Mouse-wise, probably Logitech - I have a MX Master which is great if you like chunky (also has various extra buttons, gestures etc. and can be paired with up to 3 devices). Amaze Magic Mouse users with the front-facing socket that lets you continue using it while it is on charge...
Logitech also have some interesting keyboards that can also pair with iPad/iPhone etc. and as
@HDFan noted their higher-end mice and keyboards use their "unifying receiver" so you only need one dongle (some offer Bluetooth as well, but, again, I'd double-check that your Mini supports the right version).