Chronograph is vital, after you get the basics of reloading down. Some on here never see a need for one, but you have two variables affecting accuracy: charge weight and seating depth.
The chronograph is valuable in finding the optimum (not maximum, but most consistent) muzzle velocity. After you've done that, work on seating depth.
And don't waste your money on a cheap, screen-type chrony (I fought with and cursed one foir my first 10 years of reloading); they are hard to use, and you waste a lot of shots when you get shots that weren't detected. That will mess up your statistics. You want to shoot at least 5 rounds of each charge weight, for the SD to mean anything. As you zero in on your OCW (optimal charge weight), shoot 10 rounds of each weight for more meaningful stats.
What are good stats (SD and Extreme Spread)?? Look at the threads on here.
Which brand?? Most everybody on here will agree on Magnetospeed or Labradar. (There are other long threads debating and comparing the two.)