Depending on the activity and the funder, you may need budgets showing the income and expenditure for the whole organisation and for the activity you are asking this funder to support — showing how their support will fit with the support of others or your own resources. You need to ask for a specific amount of money whether that is all the money you need, or a contribution to the whole project. Make sure that this is clear.
Once you have all this information to hand, writing a good funding application is a straight forward task.