Re: .338 Lapua Mag Die Sets
It depends if you want to re-size your brass each time. Re-sizing your brass each time will reduce the life of the brass, but will make reloading more reliable.
If you want to re-size each time, use a two die set. If you don't want to re-size each time, then use the 3 die set.
Buy a set with a Type S bushing or type S match bushing neck sizer die. This will allow you to control your neck tension which will make the rounds more consistent.
I would also recommend buying a set with the competition seating die.
The set I would buy is the Redding Compeitition Bushing 3-Die Neck Sizer Set which sells for $310.99 from MidwayUSA.com. It is expensive but at least you will not have something to upgrade too in the future.