I think that Emerson believes that every person should be as much as individual as they can. Be who you are on the inside, don't try to be like everyone else. Don't worry about fitting in, if someone is a real friend, they will like you for who you are, real friends won't dump you for being yourself.
When Emerson says "Insist on yourself; never imitate." he is saying that you should act like you are on the inside; don't try to be like someone else. Be your own person and strive to be as different from everyone else as much as you can. Emerson said that your mind is your own, and no one can touch it. You can think what you want to think, and no one can change that. He describes this belief in the quote "Nothing is at last sacred, but the integrity of your own mind." People can mess with every other part of you, but your mind they can't reach.
Emerson is quoted as saying "My life is for itself and not for a spectacle." I think that he means that each and every person has their own life to live and that they shouldn't devote their time to worrying about what other people are doing. You have enough to worry about with what's going on in your own lives.
Emerson believes that when you express what you are feeling on the inside, most people will be able to relate with what you are feeling. He tells us this in the quote "Speak your latent conviction, and it shall be the universal sense." Everyone will be able to understand what you are going through in one way or another.
Emerson really believes that society is bad, whichever way you look at it. Don't listen to what society has to say, do things on your own free will how you want to do them.
Society tells you how to act, how to dress, how to look, and how to live....