You can buy all the items that you could regularly find or earn, such as the shuriken, blow gun, colored rice, etc. There are also skills that you can buy. I am not sure about what all the clothing does, there was far too much of it for me to try and figure out.
Another aspect of it works like this. You start out with 150 points that you distribute to a circle that is divided into 3 pie sections. Red, Blue, Green. Distributing points to red increases your health bar, blue seems to be defense, and green i think is stealth or speed. As you progress you will eventually level up ( not sure what determines this) until you have 270 points to distribute. Many skills and clothes you can not use unless you have enough skill points in a certain catagory. You can switch up these skill points between any mission.
One thing that is different about this game is that there are not many bosses. Most of the bosses that there are, you can sneak up on and assassinate if you are stealthy enough.
5th in the world at cutting nose hair.