If you are shooting a flat a week, it definitely makes sense to load your own shells. One thing I didn't see mentioned (excuse me if I missed it) is that you need an accurate scale. The bushing charts are just approximations and are often not correct. Never trust what the companies say a certain bushing should throw, weigh it yourself.
Honestly before buying any components or supplies, I would start with the Lyman #5 reloading manual. There is a ton of good information in the book and it will help you understand shot shell reloading.