A little information about the NES Classic Edition
Nintendo Entertainment System: NES Classic Edition, known as Nintendo Classic Mini: Nintendo Entertainment System in Europe and Australia and Nintendo Classic Mini: Family Computer in Japan, is a miniature replica of the Nintendo Entertainment System home console by Nintendo that launched on November 10, 2016 in Australia and Japan, November 11, 2016 in North America and Europe and November 23, 2016 in Russia. Based on software emulation, it includes a static library of 30 built-in games from the licensed NES library, including some third-party titles, with writable storage only for save states. For a list of those games, you can go to https://en.wikipedia.org/wiki/NES_Classic_Edition#List_of_games. However, the system is infamous for its stock shortages, which has made some sellers of the system sell it at a higher price than its recommended retail price.
Now for some ways to improve it:
Add more NES/Famicom games (hundreds of games can be added (this hack doesn't use the same method as Play other systems on it)) - You can click here to go to the tutorial on YouTube, which will open in a new window. It lasts for a little over 6 minutes and should be easy to follow. Also, it should hopefully work on any NES Classic Edition, no matter what region or name it is, even if it's a Famicom Mini.
Make it portable - Just attach a portable USB battery to the DC In port and the HDMI cable from the console to a mini monitor's HDMI port and the NES Classic Edition is portable. Optionally, if the mini monitor has a headphone port, you can plug some headphones into the mini monitor and the headphones will work just like it would on any other device with a headphone port.
Play other systems on it - You can click here to go to the tutorial on YouTube, which will open in a new window. It lasts for 6 minutes and 15 seconds and should be easy to follow. Also, it should hopefully work on any NES Classic Edition, no matter what region it is, even if it's a Famicom Mini. With this hack, the NES Classic Edition can be used to emulate systems such as 32X, arcade, Atari 2600, Famicom, Game Boy, Game Boy Color, Game Boy Advance, Game Gear, Master System, NES (what the NES Classic Edition was designed to play, but I'm pretty sure with this hack, it would emulate the NES differently due to using a different emulation engine), Nintendo 64 and SNES, possibly with even more systems being supported.
As for items you can get for the NES Classic Edition to improve your experience on it, these are some of them (despite the NES Classic Edition being hard to find, the accessories can be cheap (some of them might also work for Wii Remotes due to the NES Classic Edition's controller ports being Wii Remote expansion ports (however, the Famicom Mini controllers are hardwired into the Famicom Mini, just like the original Famicom, presumably making NES Classic Edition extension cables and wireless controllers useless on the Famicom Mini))):
Extension cables - Extension cables can be plugged into the end of the controller that usually plugs into the console. After the plugging in of the extension cable into the controller, the controller should still plug in perfectly into the console as if no extension cable was inserted into the controller at all. Also, extension cables are available in a variety of different lengths.
USB cable to AC adapter - If your NES Classic Edition came with no way to plug it into the mains and you'd like or love to use it plugged into the mains, you should get a USB cable to AC adapter.
Wired controller - If you think one wired controller isn't enough for the NES Classic Edition and you want another one, you'll probably want another wired controller for the NES Classic Edition.
Wireless controllers - If you prefer using wireless controllers than wired controllers with the NES Classic Edition, you're in luck! However, you'd need a wireless dongle to be plugged in the controller ports wireless controllers are being used for.