I want to add green tea extract as one of the ingredients to my moisturizer, but don’t know an effective way to add it in? Do I break a capsule with it in it into my moisturizer?

How can I tell if the brand doesn’t contain pure green tea because I’ve heard most brands fake it?
Right now I drink the green tea from Trader Joe’s.
Which is the best brand?

I know green tea is high in antioxidants and that antioxidants help rid your body of toxins which in turn helps strengthen the immune system. If I drink green tea every day, will it be significant enough to strengthen my immune system?