It isn’t too early. Now is a good time, as fall of senior year gets very busy.
Pick teachers where you got the highest grades and are most interested in the subject. Teachers notice students who like their subjects and do well, even if they are quiet.
Regarding ECs, a couple thoughts. Could you do something this summer and next fall? Say, add a volunteer activity that you find interesting? (Just an aside, it is an election year, so that is an area with a lot of opportunity, for candidates or ballot initiatives you care about). But there are lots of other types of opportunities, too.
But you also should be realistic. High ranking schools care about ECs. Be sure your list includes some colleges where they are less important. Spend time this summer making sure you have a list of colleges that include matches & safeties you really like and can afford.
Here are some tips for thinking about essays. http://talk.collegeconfidential.com/college-essays/2003258-essay-tips-to-consider-p1.html