I have a 2DS with 8.1.0-19U system nand so how to I go about playing roms on it. Do I need a sky3Ds or gateway to be able to play roms or can it be done without either of those cards. I am pretty new to the 3DS hacking scene and not sure about how to proceed.
tbh, you needta invest a little more for it. In your scenario, you've got 3 choices: Gateway, Sky3DS, or Ninjhax(or however you spell it).
Basically, if you have <9.2 firmware, which your 2DS is, it's the most recommended. It has a variety of features which I can't remember.
If you don't need homebrew whatsoever, get Sky3DS. It can work on all firmwares available for now.
As for Ninjhax, basically it allows you to run CFWs such as Pasta and ReiNand and homebrew and requires the Cubic Ninja game in your region, which you can find on ebay and the such.
In my opinion, if you have the money for it, go get a Gateway. If you don't, get Cubic Ninja. If you have the money to spare, and don't want a Gateway, get a Sky3DS, as it can work on any firmware, and you can get Cubic Ninja loaded into it and run Ninjhax and allow you to run the CFWs.