You can just buy the brass and start from scratch. Some shooters then take the fireformed brass and use it unsized and others either neck size it or full-length resize it, which is like it came to you originally anyway. Depends on what your rifle likes best.
Most basic would be to take some new cases and deburr the necks, flare them slightly, prime them, load them with 70 grains of black, add a wad (.030 0r .060), compress it enough to seat your bullet so that it just touches the lands (or nearly so) and seat the bullet. Jst take out the flare and don't apply a crimp.
Use a good lube such as SPG, DGL, White Lightning or your own specially made home recipe. The proper bullet should be 500 + grains for long range accuracy.
The above is most basic and it gets funner and funner after this!
