You don't absolutely NEED a chronograph, but without it, feedback on your reloads will be the groups they print on a target. Of course, your shooting ability can also impact the size of those groups.

When you get serious about the quality and consistency of your reloads, you'll end up with a chronograph anyway. It's not like reloading components are plentiful and cheap like they used to be. If you're going to invest the money and time, you'd best get serious sooner than later.