electric (steel) strings works best with mag pups .. it's almost needed .. some acoustic strings will work .. but sound muddy . the mag needs something steel to pick up.
i use electric strings on all my builds mag or piezo
with the risk of tooting my own horn .. i suggest you try my swamp witch strings
All unwound strings are steel and work just fine with magnetic pickups. The difference is with the wound strings. With wound strings, the core is steel but the wound part is made up other metals for mass. Bronze is most common with acoustic strings. Magnetic pickups need the steel core for quality pickup. If your building acoustic with a piezo pup, acoustic strings will work just fine.