Databases can be really useful when diving into a specific topic of interest. Unlike search engines, databases are created and organized by people (oftentimes professionals) and have extra metadata attached to each entry so that it is easier for the user to limit their search results. They can be really useful when you have a broad idea of what you want to learn more about but are struggling to find specific kinds of information. Attached below are databases specifically for species, which can be especially useful when you are looking for more broad information about the organism you choose to use for your independent projects. As an example, if you go to the Birds of North America database and look up the "American Robin" you can learn more about their behaviors, diets, breeding, and a lot more. You can do this on the same database for any other bird species you are interested in and could learn more about specific aspects of their biology you would be interested in studying.
Review articles are really useful when you want to get a broad sense of what some body of literature has to say about some relatively broad or specific topic. Where a primary source in biology is often an observational study, experiment(s), or exploratory findings, review articles look at a significant amount of these primary sources and try to group and organize them in a coherent manner to give the reader a sense of what the body of literature has found and possibly where it is heading. In science published peer-reviewed review articles are mostly written by professionals who have spent a long time working in and around the topic they are reviewing. If the review article is peer-reviewed, then when it is written it is sent to other experts of the field and reviewed further by those experts before ever being published. This means that these articles are an amazing resource to learn about the subject you are interested in and at the scope most relevant for you.
To locate review articles in PubMed or Web of Science, look for the Article Type or Document Type limit option on the left side of your results page and select Review. If you do not see the Review option in PubMed, select customize and add it as an option. In Google Scholar, there is not as easy a way to limit your result to review articles but you can try adding the word review to your search.