correct order of stability of Al+,Al2+,Al3+ is
The electronic configuration of Al is:
1s2 2s2 2p6 3s2 3p1
So, it tends to donate 3 valence electrons in order to achieve stable configuration.
After loosing one electron, it still manages to get a filled sub-shell configuration, so Al+ is more stable than Al2+
Thus, the correct order of stability is Al2+ < Al+ < Al3+