Try this: First, is this a mandatory 2 gallon shop or is it a maximum $5.00 gasoline purchase shop? If it is either of these, do this:
Calculate how much gas you might need (your vehicle's mileage) in order to get to the first station on your route. Be sure your vehicle has just enough or a bit more to get to the first station.
Next, figure out the distances between each station versus your mileage. Take those distances into account before leaving home with a nigh empty tank. If you can get to each station (or at least the first few), you should be alright.
Otherwise, you must either purchase less gasoline (at $5.00 max shops) or, purchase gasoline for another customer at one of those stations (for the 2 gallon shops).
The above is the maximum benefit method for shoppers.
What I have done is simply purchase less gasoline for the middle shops (when they are very close together), or, purchased premium (this only works for the $5.00 max shops, NOT the 2 gallon shops).
For the 2 gallon shops, you may have to purchase the gasoline for other shoppers.
What not to do (if at all possible) is fill a container with excess gasoline.
Because of federal DOT regulations as well as state and local regulations, it is illegal to travel with gasoline or other flammable substances in unapproved containers.
Or, in many instances, if it is found you are conducting business and not using it for personal reasons for traveling with a flammable substance (even with an approved container), without the DOT approved placards, you could be fined or arrested.
Lastly, as my hubby says, just drive a gas hog on those routes.