The relationship between writers and agents is one of much discussion, especially among writers. Unfortunately, many myths and misconceptions have muddied the waters and, occasionally, damaged what should otherwise be beneficial to both parties as well as the lucky publishers who obtain rights to the works under consideration.
Good books sell themselves.
If you don't have one, write another one. Study agents, editors and marketing as thoroughly as you have writing. Agents cannot do anything for new writers that they cannot do for themselves, with a little study and logic. They use the same techniques for you that you can use for yourself, i.e. bundling up a manuscript and sending it to an editor. Often, in fact, writers find their agents by selling their first book themselves, then getting an agent based on the sale.