Pilot reported confusing airport taxiway markings and taxi instructions at ACY airport.

Narrative

When taxiing from the Signature ramp to the runway; ACY ground often gives confusing or misleading instructions. Aircraft are instructed to proceed via Lima to Mike to Papa and Bravo (or LIMA straight to Bravo); but in order to get on Taxiway Lima; we first must enter onto Taxiway November. When clearance onto November is requested; we are told the entrance area is a non-movement area; even though it is not marked as such; and in fact; marked with taxiway signs for November.Contributing to the problem is an airport diagram that does not accurately depict where Taxiway November actually starts; or that the ramp we park at even exists. The diagram does not depict Taxiway November as starting at the entrance/exit to the Signature ramp; but only depicts it south of the entrance/exit. The conflict between what pilots see on the ground; how the taxiways are marked; and what ATC directs can be confusing.Additionally; the taxiways surrounding Mike and Lima intersections can be quite confusing; especially in low visibility situations. Recommend the airport paint taxiway signs to help pilots maneuver appropriately. Mark taxiways more accurately.