to make your owns patches you need to know a lot of assembler...
it's not easy, it's very hard...first, try to learn to porting patches, it's least hard but not easy anyway

other thing that it's easy is making patches to changes the paths of the files in the FS, like the drivers, flashmenus, etc.

example: a patch to change the path of the Flash Menus from tpa/preset/system/desktop/flash to card/flashmenu

for this only need the WinHex or UltraEdit or the program that you wanna use

Regards