[zoncxs]

First, you need to list the emotions you want to draw power from. To make it easier for now lets use the Lanterns (ignoring life and death and the ultras).

Thats:

Love
Compassion
Hope
Willpower
Fear
Greed
Rage

Next, How close must you be to the source for you to be effected? We also want it to stack, the more people near you that feel the same emotion, the more of your power you can tap into, this should also allow for further range too so you can get effected by the whole world if something like that happens.

Then, what powers do you get access to with what emotion? You should have a "base" power that you have when you draw on the emotions of those around you, plus a specific power for each type of emotion.

After all that we can start to fine tune everything to fit your budget.