I got Rxtools to work but I can't use emunand as it goes black when ever I press Y...
SO, you are trying to settup exmunand with rxTools.
I don't know exactly how to proceed, since i used a gateway to create the emunand, then i just add rxTools. Try to find a guide about installing rxTools with emunand without flash cart.
How would I go about making my own GBA VC? I heard it doesnt work with GW emuNAND as of yet - is that true?
As far as i know, it works with GW. At least it worked when i was on GW emunand 10.3. I've not tried et on 10.5.
tutorial : https://gbatemp.net/threads/release-agb_firm-signature-patcher-gba-rom-converter.390313/
You'll have to install a specific CIA into your SYSnand.
Then you'll have to install the GBA game (previously converted as CIA using Simple GBA Converter) into your SYSnand.
In order to play the game on emunand, you'll have to install the same gba cia game into the EMUnand.
Make sure you understand everything you do.