Start with how much pressure you need at the sprinkler head (Spray is 30).
Then Work backwards and add all of the pressure that you lose through friction loss of the Meter, Backflow, Valves, Elevation changes, Mainline, Lateral line Piping, and Fittings. This friction loss will depend on how many gallons per minute you are flowing through each valve. Usually a fairly safe number with low friction loss on 1" mainline is 12 Gallons per minute. You will have to do some calculations.
In my area a Flat Houston, a spray sprinkler system normally has a design pressure of 45 ish LBS.
I may have left one or two things out that I can't think of now, but for your purposes this should suffice.