We adding a panel box in an outbuilding, can we run it from the sub panel box in the garage or do we need to come from the main breaker box, all sub panel boxes are being used for only outlets and lights

You can feed the subpanel in the outbuilding from the subpanel in the garage providing you have room for the new breaker in the garage subpanel and you are not going past "the six switch" rule. If there are more than six breakers in a subpanel in a separate building from where the main panel is located you must provide a main breaker in that subpanel. The same applies for the subpanel in the out building. Although you are permitted to use this method I personally prefer running a separate subfeed from the main panel.