Propellor selection on an electric is a tad bit more critical than it is with glow.  But the selection process is about the same.  You have to make sure that you don't over prop it because you will quickly burn out either the motor or the ESC, or both. 

But, with that said, if you carefully select a range of propellors, based on wattage (which is based on weight and desired performance) and buy one of each.  Don't worry about having to many because if you are like most of us, you will have a good selection of props of various sizes before long and you won't have to go through this too often. 

But, what you have to do is select the prop you want to try, make sure it is within the range that won't over-burden the motor and esc, attach a wattmeter to the power path (Wattsup is a good one to  use, but I'm sure there are others) then run the motor up.  Check to make sure you are within the current/wattage ratings for your application, then put it up and fly it.  You will quickly see if you have the right combination for your airplane.</p>

I know that does not give you a specific, but you have an idea already as to what you want to do.  Now it becomes a trial and error process to select the right one for you.</p>

CGr</p>