A:Answer Hi there! I recently bought this desktop (fabulous by the way, my kid loves it!)
I attached a monitor to my answer but just in case it doesn't attach, it's on Best Buy: ASUS - 24" LED FHD FreeSync Monitor - Black
Super great quality as of now (haven't seen issues), it's under your budget for sure! No extra adapters really, it comes with everything we didn't have to buy anything. HDMI & audio cords all came with and connects just fine to the desktop.
The only thing about audio is when it plays out of the monitor itself, it sounds fine, just quiet for us but overall not too bad. Because we wanted a crisper sound, we bought some speakers from Amazon, connected, and definitely came out louder! However not required :)
Enjoy!