There are some good tips on here,
But as far as timing lights go,don't get a dial back type.The Sears or MSD are the ones to get.The dial back type are not very accurate.Just about any serious dyno facility you see will not have a dial back.
I personally am on my second Sears "cheapy" unit.The first one lasted 22 years but had been dropped one too many times.
I am sure there are other timing lights that are decent,but these are what I know work,and what other reputable builders I know recommend.
Keith