What can be the best dropout value and the FC layer for good accurate predictions?
In the area of Neural Networks there isn't one right value that works for all kinds of situations. You just need to repeat experiments, till you reach a satisfactory value. Ideally Dropout values range from 0 to 0.5 . I would use a dropout value of .3 or .2 in my neural networks. Also, the number of neurons in FC layer, impact the degree of fit in your network. Too small numbers, result in underfit. Too large values, result in overfit. Keep on increasing the complexity of the model and evaluate  it against a validation loss, that will inform you about increasing or decreasing the number of FC layers.