Green tea is traditionally drunk on its own, with no additions as most green teas have a delicate flavour, and the taste would be spoiled by adding milk add sugar etc.
When I drink green tea, I usually put 1/2 teaspoon into a mug and then add hot water, (boiled water that's been allowed to cool for a while) and allow to brew for a couple of minutes before drinking. The same leaves can be used a couple of more times before they loose their flavour.
If you're trying green tea for the first time I'd suggest that you just start of with a small amount of tea and gradually increase the amount until you get the strength you're happy with, but don't use more than 1 teaspoon or your tea will be too strong.
There are a great variety of green teas, so if you buy some and don't like it try another type.