Being in the hunting and shooting sports since the age of 10 which was to long ago to think about,I naturally progressed to the art of reloading my own ammo for every center fire cartridges I own and stocking up on the necessary components to do so for many years to come,I make it a point every couple week to add to the supply.
Cartridge conversion are a good thing to keep in mind,I do a few mainly because the brass is either insanely cheap or free to pick up all day long. As mentioned .308 or .06 or there military versions work well for many different rifle and some pistol calibers. I convert LC 7.62 x 51 brass into .300 Savage case the difference is $8 per 100 and a couple hours at my hobby vs $28 per 50 factory cases,I also convert all that free 9mm people leave lying around to 9 x 18 Mak brass plus I use it in my 9mm also.
Another thing to look at is cast bullets,either cast your own or buy commercial,either way you will cut your reloading cost quiet a bit from just shooting jacketed bullets it all depends of if you can get free lead and the powder type you use and how much. Take Alliant 2400 for instance I can load all my rifle rds. and two different pistol rds. with one powder both right at or just under 16 grs. per load,there not the speed burners there copper jacketed top dollar counterparts are but there close and they shoot as well as and often times more accurately,kill small game up to large deer,and it will knock the smile off a two legged critters also.
Rounds I cast for,54r,300 Sav.X39,357/38,9mm and 9 x 18 Mak.