For a fairly new shopper I would encourage having no more than 1 shop on your route that you have never performed before. Be prepared to give it plenty of time because if you have not done it before you really don't know how long it will take.
Now see what you can find that can be done on that day and self assign or request them. Plotting your route is actually a fairly minor part of the whole process. You need to check times to make sure you are set up to arrive at the right place comfortably within the window allowed for the shop.
So your first step in planning a route should be looking at those companies with whom you have already worked and seeing if you can line up shops you have done already in areas that will sort of flow together. When I am doing a route I generally am going in a particular direction. In the past few days I picked up a large number of shops that broke very nicely into one trip mostly east of me and then a large circle that started NW, moved W, moved S, moved E, moved NE and finally back home. I was able to incorporate locations that were 30+ miles from me because they were 5 miles or so from the previous stop. And I knew that I would be exhausted before I finished the circle route so planned a couple of possible break points to come home where rejoining the circle the next day would be easy without driving miles and miles out of my way.
And the real trick to routes is to make good notes as you go and drink plenty of fluids, especially in hot weather. We are still in the 80s here, so about the third stop on any route for me is to pull into one of the gas stations that offers any size drink for 69 cents. I get the largest drink possible and make it mostly ice. I will consume the soda fairly quickly and then can start pouring my bottles of tap water onto the ice to continue having cold fluid. I am not a big snacker, but without plenty of fluid I will wilt long before the job is done.
The better you know your area, the easier it will be for you to figure out a route of local shops. Anticipating when rush hour will be and either taking side streets or going against the flow of rush hour traffic can save you lots of time. Certain corners have lots of fast food and other eateries. These areas are usually mobbed at lunch hour, so I try to work around them and land there well before or well after lunch. All else being equal (which it rarely is), I try to do right hand turns as much as possible. Not only is it safer than crossing traffic, we also can turn right on red after stopping at most intersections here.