You mention that A is a teacher at the community college you attend? I realize that you seem to know him and E outside of the college as well - the club you mentioned. I hate to be the cold water thrower but colleges often have fairly strict policies about teachers dating students. Yes, you are all adults but the presumption is that an potential power imbalance exists. And it may not matter if you never take a class with him at least in how the policy is concerned. An 'affair' with a student could really hurt him professionally and it is risky for you and E socially and professionally as well.
And I am curious if you have dated people not in a couple? I wonder if you have dating experience outside of being interested in a couple. Dating a 'singleton' is very helpful experience in dating, period. Dating is hard in general, relationships are hard in general) but you are leaping ahead orders of magnitude in difficulty. If you haven't dated someone before, been in a couple yourself, well, I'm going to be the old fart and suggest, maybe, you want to walk before you run.