There are two efficiency to consider: The first is mash/lauter, the second is total brewhouse. Glad to hear you have your own mill! It sound like your gap is good. just be sure you have no whole grains and everything is in fact crushed with some flour.
Second: 1.25-1.5 qts per lb of grain is ideal for mash in and you will lose about .12 gallons per pound of grain to absorption which is considered a loss as well as any dead space in your tun. You also need to know what pre-boil volume you are looking for to calculate how much volume to sparge with.
Be sure you are using a good calibrated thermometer to ensure you are mashing at the correct temperature. Also be sure you are stirring well at dough in to be sure you are not getting dough balls and unwetted grains. Some people like to stir half way through the mash as well.
When sparging it is important to stir like hell prior to vorleuf/sparge. If you do a two step sparge you will need to stir like hell again, vorluef and drain.
Now, mash/lauter efficiency tells you how well you mashed. You need to take a gravity reading once all your wort goes into the kettle, prior to boil. Temperature corrected! This gravity should be about 10 points less than your estimated OG reading. If it is lower than that your mash process needs improvement. If it is higher than you have a good efficiency at this level.
Total brewhouse efficiency takes into account the final post boil, chilled gravity and this will be a function of both the lauter/mash as well as meeting all your required volumes. In other words if you get too much wort in the primary you will have a lower efficiency due to dilution, higher means you over boiled and concentrated the wort.
Hope this helps! If you are not using brewer software I would recommend it! Helps a lot.
Edit: Brewkinger is a much faster typer than I am