Claiming facebook page vanity url

Hello. This is the the first time I'm creating a facebook page. I'm confused about facebook urls. I couldn't use any url I wanted, even though they didn't exist and it's unlikely anyone ever registered it (a combination of my brand name which doesn't exist yet and a generic word related to my niche). So I just typed something like "dgdgestgesrgserg" and the page was created with that url. I searched for a way to change the url, but it seems it wasn't possible. So I deleted the page and created a new one, except this time I didn't get to choose an url. Facebook did it for me with something like BrandName-43463634535 . I searched further and found this article: https://www.facebook.com/notes/equi...y-url-for-your-facebook-page/474147772600069/ and it seems I have to have 25 likes to change the url. Except I didn't get informed about it, other than having myself find it in google search. So what should I do, keep that name, wait for 25 likes and hope I will be able to change name? Will it affect seo negatively, due to change in the url? I don't know how fast I'm going to get these 25 likes.

From what I've read, I should go to facebook.com/username , but on this page I can only change my facebook profile username. Will the option to change page username appear once I get 25 likes?

Also I have no idea, what username should I choose. The options seem to be so limited, I wonder whether it is worth it. My brand name is taken by an empty page, and 2 other urls, which were a combination of my brand name and generic words, were also taken, but don't exist. The only thing that comes to my mind is to use brandname.com, don't know if they will allow my to take it though.