Your question lacks a lot of information.
Do you intend to buy 100 bullets at a time or in bulk??? If you buy a couple of thousand bullets in bulk it can be almost as cheap as surplus without the hassle of pulling the bullets. If you are just using it on paper or to plink the lighter the bullet weight the cheaper the bullets.
Then of course there is the option of cast bullets with gas checks that are available from several commercial sources like the bullet barn.
Bulk is the way to go. Then of course you have to find a good supply of brass and learn how to take care of it so you can get lots of reloads out of it.