There are loads of ways to do this. For the basics :
Create coin at x=0,y=placeY, add 1 to groupnum, add 25 to placeY, run Function CreateCoin
That will create 8 coins that are in a straight line upwards, 25 pixels apart.
You could also create and add to or subtract from placeX rather than X=0 to move them across the screen slowly.
Based on the values you are adding to or subtracting from X you could expand this into more functions called 'CreateLine(the example), CreateLeftToRight, CreateRighttoLeft' to call different patterns. Each function could run based on a random number you 'choose' and therefore each shape of coins would be chosen at random.