The importance of the first draft is to test your outline and structure to see if they work. As you start your first draft, do not get caught up on the details just yet. Do not worry about having the most creative Introduction or a fully developed argument. It is very rare that a writer will write the perfect draft on the first try. The importance of the first draft is to try to get your ideas out based on the outline you have created. It serves as a reference point to build off of for your later drafts.
For most writers, the Introduction is the most difficult part of the whole essay. For the first draft, it is perfectly acceptable to only have a two sentence long Introduction and to dive more immediately into the argument. It is simply difficult to know how to set up your argument if you have not started it. So, in the first draft, do not give the Introduction priority. After the first draft, you will have a feel for your argument and can start to develop the Introduction. The Introduction should included:
Body paragraphs are the meat of your argument. Body paragraphs are the explanations behind your thesis statement. It is important that your body paragraphs support your main idea and thesis. Each paragraph should argue one main idea and have supporting details to back the main idea. A body paragraph's structure may look like this.
Topic Sectence (a main idea of your argument)
Another example:
I like dogs (topic sentence)
In the pargraph, one main idea will be discussed, and the topic sentence will introduce the main idea of that paragraph. After the topic sentence, the supporting details will reinforce the main idea of the paragraph.
The Conclusion has to serve many purposes for your essay. A conclusion restates your introduction and thesis, but it does not repeat it explicitly. The Conclusion also serves to put your argument into a big picture. At the beginning of the essay, in your introduction, you tell the reader what to expect in your paper. Then, in your body paragraphs, you provide your argument and the supporting details. In the Conclusion, you are putting the final touch on the overall argument by summing up the entirety of your argument. This is not the time to introduce any new material. It is a time to restate your argument and thesis.