There is no way I can tell you which will work best for you. Price may be a factor -aluminum molds are frequently less expensive than steel. If you buy a Lyman or RCBS mold, you will need to get handles. As purchased, molds will need to be cleaned. After they sit for a few minutes, I swab them out with a cotton swab dipped in acetone, until the swab comes out clean.
Several outfits sell a fancy caster's mallet .
I have used hammer handles since I began casting. Never strike any part of your mold with a metal hammer. I buy hammer handles at the hardware store. Flux can be as simple as a pea sized ball of wax or as complicated as a two part commercial flux that requires a fume hood to use. I usually use Marvelux -it doesn't smoke like many of the other fluxes do.