I know you two are both new, but 100x100 is the usual size for avatars now...
If you have 30 posts AND have registered for 30 days, you can give yourself a custom title and a custom non-animated avatar. The dimension limit of custom avatars is 70x70 pixels and size limit is 4 KB.
If you have 100 posts AND have registered for 100 days, you can give yourself a custom non-animated avatar up to 100x100 pixels and 6 KB in size.