Welcome Cheuk. I don't know what your flying experience is. I have never flown a real plane but before joining EHM I was flying full time on Boeing 737/767 and ocassionally on Airbus, very rarely on turboprops.
At first I was a bit taken aback at having to start from zero (like the real pilots) flying the boring and slow piston a/c

But believe you me, it is worth the effort of going through the progression. I am currently on the mid of my Class 3 rating (Senior Turbo Prop Captain) and can't wait to get my hands on Class 5.
Anyway, I would suggest you the Beechcraft of the Sukhoi on Class 1. On Class 2 I suggest you the Beechcraft 1900D.
On Class 3 both the ATR-72 and Dash 8 are good, only the ATR's cockpit seems to have been vandalized and left without the covers of the walls (same on the FSX version).