I think you'll be loading the shot by hand (i.e. I don't think the shot bushing will work with buckshot)
I'd make a shot counter - a board with some dimples in it equal to the number of shot you need for your load. Easy way to count out pellets.
As said above, standardize your hulls and don't mix recipes. Don't buy a bunch of components and then try to find a load for them. Figure out a load then go find the right primer, hull, wad, and powder for that recipe. Generally the powder manufactures have pretty good load data on their websites.
Ponsness are very good loaders. The 375 is a nice single stage press. Compared to the other press they are built like tanks.
Also, ponsness makes a shot and powder measure kit that makes catching powder or shot easy without removing the die and hull from the press. Ponsness website is www.reloaders.com.