Some pickups are pre-staggered for you, eg: Duncan’s SSL-1 Vintage Staggered so you won’t have to crack your brains out as to how to do it. The down side of it is that, these are flat pole pieces, which means that their pole pieces surface isn’t the slotted type so that you can raise/ lower the stagger yourself.
So is the stagger a necessity? It depends on your preference. If you wish to have a more balanced output from each string then this might do the trick, as per Fender’s philosophy. Otherwise, start flat out & raise the pole pieces to your preference.
Do take note that when you raise/ lower the pole pieces, some wax might be dispensed. Some luthiers are of the opinion that this might induce microphinics but IMO the amount is too negligible to contribute to this setback.