how many sources one can use as evidence in their research
As you follow citations and see all the research that is used in one scholarly paper, you begin to see how scholars work across disciplines.
how much info Google Scholar has
Google scholar is good for following citations from a known item - you have the title and author, for instance. It is not great as a discovery tool, in helping you to find research about a topic. This is because the search doesn't allow for much narrowing.
What questions you had:
Format of citations?
I can't tell what the question is here, but I can say that there are hundreds of citation styles and they are specific to the disciplines you see them in. Each discipline decides what the most important information is in the citation and builds the style from there. Additionally, some disciplines tend to cite a certain type of information (journal article, book, site report) more than others. As such, they need to construct a style that is clear and consistent for the audience.
How do you find articles for your topic in general?
Use the Databases I Recommend page at left. The databases are good at allowing you to search specifically for broad topics. The Libraries provides access to about 800 databases, all with different info. As you become comfortable within your major, you'll find you'll only use a small handful.