Hello, the DNA test that you choose will depend on why you want the DNA testing. Here is the link to DNA testing that you can get from Family Tree DNA testing: https://www.geni.com/dna-tests?tracking_source=dropdown-header-link. This link is found under the Research selection in the top ribbon on your Geni page. I tested my DNA with Family Tree and am happy with the results.
There are several DNA tests you can take. For example, mitochondrial DNA will reveal information about your maternal line only, since we all inherit our mitochondrial DNA from our mothers. Y-DNA is a test for males only. Men inherit their Y-DNA from their fathers, so this test will reveal information about your paternal line. Autosomal DNA testing is used for when you want to find relatives, including cousins, usually up to about 4th cousin.
I hope you find this helpful. Please let me know if you want more information or clarification.
Best regards,
Noelle