I am using the default 2gb card that came with the console. It works fine when I launch gateway mode but when I open the settings it's almost as if it resets it and it exits gateway mode...I'll see if I have another SD card but I don't think I do.
1) Default 2gb sdcard is too slow for emunand, so you have to use another one.
2) When you exit settings, 3ds gets soft rebooted so it loses Gateway Mode features. You have to boot gateway mode again every time you exit gateway mode.
3) About installation process, if you want to use latest firmware, you must create emunand, because if you update your systemnand, even if in gateway mode, you will lose Gateway support.... So, if you want to install emunand, do that:
-Backup your SDCard on your computer.
-Open gateway menu (DS profile+ L) and select "format emunand". Now your sd card will get formatted.
-Now, if you boot gateway mode, it will automatically load emunand.
-Put your sd card on computer and copy your files back to your sdcard.
To update, do that:
-Open Gateway mode (emunand), go to settings and set up wifi connection.
-Exit settings. You come back to sysnand.
-Now, remove wifi connection from sysnand.
-Boot emunand. Open settings and when you're sure that there's " GW3D" near system version on the top screen, you can update your console.