The most easiest thing to move with a Ki blast is... toilet paper. Yes, that common household object is the easiest thing to move. Just hang it down lots from the roll and fire a Ki blast at it. If it stays continously moving, you have done it correctly.

 

The next thing to move is a floating balloon. Fire a Ki blast at it and it should fly backwards a bit.

 

You can then go onto thicker objects. The thicker they are, the harder to effect them. Example: A wall. Since the wall will not move back, it disturbs the wall's molecular structure and makes hole in it with the shockwave of the Ki blast.

 

If you have a pet, you could try it on that. But beware of doing it on small animals, as they only have small lungs. And that will be terrible for fluffy the hampster :).

 

Eventually, you could try it on humans. Your friend would be an ideal person to pick, as he/she would be understanding. But beware, if the Ki blast is powerful enough, it will feel like a pole has been rammed through them. They might feel tingling if you do it on skin. Do the Ki blast on bare skin (stomach has the best effects) if you can. This works better because your clothes' aura absorbs a bit of the Ki so it is un-feelable.