What is the best way to start an anthropology career?

Anthropology and Ethnographic research fall under more professional fields than people give it credit for. Yes, there are options to become a professor, or museum curator, but those are not the only options. As far as specifically observing Native American tribes and other co-cultures (be careful with the word subcultute, it identifies the subject as beneath the other/demeaning) there are nongovernmental organizations that may do research on the subject matter, but you will probably find more labeled as domestic issues. From the domestic issues in the U.S. subject you would have more room to find something in the field that could focus on Native Americans. There are other options, such as consulting with the UN or with another organization (even think tanks like CSIS or Brookings) to further help look into the subject matter. If you want to take time to research before finding a full time job, there is Fulbright scholarships that you can apply a subject of research to and spend X-amount of time to research. You can submit a subject that you want to focus on and will need to submit a package on the subject. There are other titles such as Research analyst, Policy analyst, Qualitative/and Quantitative researcher, Human rights associate, and so on. Also check into fields like conflict analysis and resolution, many people within that realm do ethnographic research. I have done ethnographic research in France as a conflict analyst/policy analyst. Internships will definitely help and give you an advantage when you graduate. I believe you found a niche subject that should have more research associated with it. Do not be discouraged, sometimes you need to play with the title wording and even take a chance to find the job that will fit you best. Cannot wait to read your work one day!

Fulbright: https://www.cies.org/program/core-fulbright-us-scholar-program