I got a client to 1st page on a competitive keyword, now what?

Hey everyone,

I was able to finally get a long term client of mines on to the first page for a keyword critical to their business but nationwide (despite the business just being local).

Now I want to know, how can I take this and promote myself accordingly?

Can I make a case study off one keyword? Should I add this into an existing case study as proof of concept? Should I add this on my resume?

This is important since, things are dry over here, so I need to capitalize on this small win. Please help, thank you!