Conditional Logic

Please i want to have a conditional logic where one field can only show if a given field is selected or value typed.

e.g, if a user select “Money” from a given drop down menu field, then another field which says “Type amount of money” will show, but if he select “GOld” from the drop down menu then the type amount of money field will be hidden and a field called “type Gold Karat KG” will show.