Many earlier psychoanalytic approaches to literature tended to analyze characters and/or authors in terms of such Freudian concepts as the id, ego, and superego. The id was often associated with emotion, the ego with rationality, and the superego with morality and/or conscience. Characters and/or authors were sometimes interpreted in light of conflicts between these three aspects of the psyche. This may give you something to go on as you begin to think about the poem you have in mind. For sophisticated criticisms of Freudian ideas, see the work of Frederick Crews.
It would be extremely helpful if you could give us the poem to which your question refers so we can give you direct answers. Marxism normally relates to consumerism by attacking it and seeing it as another way in which the lower classes of society are kept in their position by a dependence upon expensive luxury goods that they are made to believe are essential for their lives. However, without knowing which poem you are talking about, I can't really help you more than this.