How Can I Leverage My Results Into More Clients?

Hello Everyone, here's a little background on my story and why I want to leverage my current results into more client.

Currently I have roughly 4 clients that I work with month over month on SEO, and on top of that I have a few lead generation sites in the works. Now my results for both the lead generation sites and the clients have been pretty solid with some of them ranking on the first page and others on their way to it; however, I really want to build up my agency by landing more clients and I figured the best way to do that would be to showcase my previous results in someway that would make a customer see that the proof is right there. I've tried to do this in the past, but often times I lose interest either before I can show the results or when I explain that SEO is a long term game and may take months or even years depending on the industry to generate those types of results. Is there a better way I could be showcasing my results?