3 teaspoons is roughly ~10-12 grams of tea, and in 100ml of water, you must
try at least 5 steepings. I like to do a lower temperature wash (75* for ~20 secs) to open the leaves, and then steep in "near boiling" water 30, 30, 45, 60, 1:30, 2:00, 5:00, etc.
I'd also try using less
leaf and see if you notice more of the subtleties of the tea. I enjoy a 1:1 ratio for Japanese greens and certain blacks, but I seem to get a better "feel" for the tea when I use 1 heaping teaspoon in my 100ml gaiwan.
Also, are you using one of those button gongfu pots that dumps all of your steeped tea into the bottom of the jar (like this
)? If so, I'd recommend drinking each steeping of the tea by itself (if you have the time) so you can taste how the tea evolves over time.