Make a citra emulator

Can we make our own citra emulator build

yes the guides for building citra is on the wiki

What can we add to the emulator?

what ever you want, considering you know how to code it/ there is already a code for it somewhere

How do I get the codes?

idk, write one if you know

You clone the source code with Git, modify it and follow the building guides.

Please refer to our building guides:
Building For Windows
Building For macOS
Building For Linux

Msvc or mingw? Which is better

MinGW is a bit faster.