I often buy green tea with different flavors like lemon, strawberry, and jasmine from the market. I want to add these flavors at home. Can you recommend how I might do this?
Depends on the flavour I suppose. For the most direct route, I would try just steeping the fruit/flavour in the tea/water for a bit (ie: sliced strawberry, sliced ginger, lemon zest/peel, etc...). I make a ginger/lemon "tea" with thin slices of lemon zest by just steeping it in water. No reason you couldn't add some green tea leaves to that as well. Lemon Juice, I add before serving.
As mentioned finding an extract could work as well. No idea about amounts, you'll have to do some research as to what is safe/appropriate. I haven't used them.
For a Jasmine Tea, I would probably just find a good tea purveyor and find a proper Jasmine Tea.
Blending tea recipes yourself should potentially taste better than what you get in a pre-blended tea. If you buy a flavoured strawberry tea, there isn't much real strawberry. Instead, it's artificially flavored.
What you have to keep when adding fresh fruit to your tea, is to steep the tea without the fruit first, and add the fruit (juice) later. However, when you infuse fruits in dried form (jujube, goji berries), you can steep it together with the tea at the same time.
Besides fruits, also try to experiment blending different types of tea (green, black, oolong, pu erh etc..) with non-fruit herbs such as chrysanthemum, lily, and honeysuckle flower.
I've published a few recipes for which I'm not sure if it's appropriate to share the links here. Just message me for the details!