Recent versions of GDB are Ada aware and capable of debugging Ada programs compiled with GNAT. If you have an older version of GDB in /usr/bin that isn't Ada-aware, I'd recommend just updating your GDB. If that's not an option, you'll need to add /home/...(my stuff) to your PATH variable before /usr/bin.
Another option would be to use a function or set an alias in your .bashrc so that the command gdb calls the version in your home directory.
alias gdb=/home/...(my stuff)/bin/gdb
Of course you could just call it using the full path.