As a newcomer, let me try.
I think it is:
Without me, you'd be angry and sad.
Once you lost this emotion on your decision, planning or expect, you might feel angry or/and sad.
With me, I help form a triad.
For the Honor and power, Greed can let you raise from a triad, which triad means the branch of Chinese organized crime.
I'm not 1, not 7 but somewhere in between.
On the concept of Seven deadly sins, Greed is the 3rd.
In very few cases I won't be seen.
Tons of criminal cases because of greed.
To solve this riddle, now proceed...
Greed "encourage" us to find the correct answer.
You'll see me when you've done the deed.
You feels good once helping the others, it "encourage" doing more and more, affected by a little bit of Greed. (Too hard to explain :P)
You will know my number from 1 to 7 with light and some water.
You can see your own face since most of us has "Greed" as a Human being.
Just try to answer, please forgive my horrible grammar as an Asian.