Here's the information we found about 5th-century Gothic names.
We were able to find a list of male Gothic names from 300-600, included at the bottom of this letter. (1)
Almost all Goths used a single name, and we recommend that you do the same.
However, if you want to register your name you'll have to use some kind of second element. For the purposes of registration, you could add a second, shorter name--there are a very few examples of Goths with two names, and in most cases the second name is short. However, in daily use it would be historically accurate to use only one name.
Talan Gwynek, Arval Benicouer, and Pedro de Alcazar contributed to this letter.
We hope this has been helpful, and that we can continue to assist you.
Academy of S. Gabriel
(1) Woolf, H. "The Old Germanic Principles of Name Giving," ch. XIV