I was gifted a 5 gallon bucket of walnut shell media several years back. I still have a good 4 gallons left. Works good, and will probably out last me...
I've used a Dillon 550b for almost 30 years and I've replace two parts on it that Dillon sent me for free. I recently bought my second 550 and now have one dedicated to large and small primers.
Loading bottle neck rifle rounds is much more time consuming and complicated than straight walled pistol cases.
I would start with pistol cases.
These days 9mm and .223 are so cheap they aren't worth reloading for your typical range practice however it your doing serious precision shooting then reloading them is essential.
I'm set up to load everything I shoot and almost enjoy it as much as shooting.