The amount of sleep you need daily is different for each person. You have to experiment with different amounts of sleep, and take note of the amount of hours that made you feel most rested.

A good base to start with would be around 7 or 8 hours. Try each out for about a week and asses which was better for you. Repeat the process if you're still not satisfied.

Also keep in mind that the amount of hours you rest for, doesn't speak for the quality of your sleep. 

Try to refrain from having any caffeinated drinks before bedtime, or heavy meals. Using your mobile phone/tablet before you go to sleep is also not suggested, as it emits blue light which your brain compares to natural sunlight and keeps you from feeling sleepy. If you absolutely have to use it, try a blue light filter.