each have distinctive characteristics and flavors. i've used irish breakfast tea, and its fine. you just want tea- no flavorings, especially teas like earl grey. most any tea will do, just so long as its tea. (i have however, brewed St. Dalefor organic mango green tea, and that doesn't seem to inhibit good brewing.

i have found from my own experiments, that if you cook up a batch of goji berries (in glass), and cool and strain the liquid, and add this to the brewing tea, it enhances the process, and makes it more potent, in my opinion.