Some kind of holder for premeasured shot charges is handy. You can buy em or make em, depending on your interests. I've got both homemade and storebought and use them sometimes.
I gotta add though, that there's no ONE answer for all people and all situations. I shift back and forth between a horn and premeasured charges depending on the weather and where I'm hunting.
What I'm saying is, the premeasures are a good place to start, but you'll probably keep shuffling around like the rest of us, trying other stuff, too. Even if you come around to a horn or flask later on, it's likely you'll still find uses for premeasures.