how many layers of pcb i need to draw?
Assuming that you are a beginner, start off with a simple circuit on a single layer. Do as much as you can on a single layer. If you feel that a single layer is not sufficient, move onto two layers but preferably distribute the network across both layers instead of allotting them disproportionately with so much more on the first layer than on the second.
Irrespective of what the application is, keep this in mind: try compacting the circuit and keep the number of layers to a bare minimum.