Depend on how good the wall or should I say plasterboard is!
the easiest option is to use such as Toggle Bolts but a better option is to help spread the load and weight by gluing (cover the entire back of the board, not just dabs here and there) a wooden panel to the wall, say 15mm ply and smaller in H&W than the back of the TV so it is hidden when the TV is mounted.
You can then screw the TV mount to this board. Note that you don't have to use 15mm screws and can (and should) use suitably longer 'parallel' shank screws to get a good grip, etc.
Cheers
Starb