The number of times per week you spend practicing is less important than what you practice. If you aren't working on the right things then you will just be ingraining faults. If you are looking to improve your game then you will probably need to spend at least an hour per day working on something whether that be putting, chipping, pitching, full swing or fitness. If you want to get onto the professional tours then you will probably need to be working on your game as a full-time occupation!