If you breast feed you don't need to do either because BF poop is water soluable. Once you start solids or give a good deal of formula you'll need something. There's definitely a good chance you can just use the liners and won't need a sprayer. If you end up not liking the liners (like me) you might opt for a sprayer instead (like me).
Re: Diaper Sprayer
You won't need it until you start solids.
We just started solids, and I still don't know if we need one or not. Go back a page or two and there are other posts asking this.