Ancestry DNA is an autosomal DNA test and will provide an ethnicity breakdown. It will also show relative matches to anyone in the database whom shares DNA with you. All of your family lines will be represented. It doesn’t matter about the gender.
Everyone receives approximately 50% of their DNA from each parent; 25% from each grandparent; and so on and so forth. Autosomal DNA will provide matches reliably up to 5 generations. However, it is not necessarily unusual to have 6th, 7th and 8th cousin matches too.
Connections to people with the same DNA will enable you to expand your genealogy tree. DNA can also connect you to your birth parents or help you confirm where your great-grandma immigrated from. It can introduce you to relatives you have never heard of or lead you to that lost branch of the family that you have always wondered about. You never know what you might find.
If you still have your parents and they are willing, test them BOTH! Even testing one parent will beneficial. And it is also a good idea to ask their siblings, aunts/uncles and your grandparents. Testing multiple relatives goes a long way in isolating family lines. Also, always test the oldest generation first. Not only do you not want to miss out on the opportunity, but they are generationally closer to your ancestors and will have matches that you do not have.
Ask your siblings to test. Even full siblings will have different matches beyond 2nd cousin. You will likely even see differences in their ethnicity breakdown.
Upload your raw data to GEDMATCH for FREE. Why? Unfortunately, Ancestry DNA does not provide a chromosome browser, which is a very important tool in genetic genealogy. Also, you will generate matches from 23andme and FTDNA, whom also uploaded.