Link to where you bought the reader. I was about about to order the one of amazon to get mpg read outs.
My friend's mechanic recommended that particular one to me; it is also the most popular one on Amazon. He actually uses it more than his super expensive Snap-on OBDII reader. I have had absolutely no problems with it and it works perfectly with Torque; don't believe the negative comment, unless you have an extra $160 to burn.
As far as the paid app goes, it only adds minor things such as diesel engines and a larger selection of graphics; however, I will eventually upgrade just as an appreciation for the amazing work that was done with this app.
For mpg I set up mine up as follows. You can have dials on multiple screen pages, all customizable for type of sensor, size of display, etc. I set up one screen that shows six displays (Average mpg, Instant mpg, Trip mpg, Trip in miles, Engine revs in rpm and Speed in mph). On another screen I have one full screen size indicator that just shows Instant mpg, so it is easier to see. My third screen has a bunch of other indicators that I change around just to play with different sensors. My fourth and fifth screens each have one of the widgets which are also available.