How much time do you want to spend each week on your English? Remember, if you are going to succeed, you need to make a plan. You must stick to your plan. Make sure you can actually spare this amount of time. Be realistic.
Think about these things:
Do you work full-time? If you do, when are you free to study?
Do you have a family? When do you spend time with your partner/children?
Are you studying full-time? If you do, when do you have free time to study?