If you know a lot about your family history and have relatives that can help you build your family tree, you may not need a subscription to a genealogy website. If you have information to go on, you can find useful resources online that can be accessed for free, such as some Census records.
However, if you only know a few generations of family history, and you're serious about creating an extensive family tree, you’re likely to benefit from a subscription to a genealogy website. Ancestryhas access to over 27 billion historical records online, which includes more than 13 billion ancestral profiles. Plus, Ancestry offers a two-week free trial, so you can try it out risk-free.