During my time as a PT, I had a website. I did not get as many views on this as I did on my Facebook page, but it did give a much more detailed overview of what I offered. I found that potential clients who found me on my website were a much stronger lead as they had to go searching to find me, whereas Facebook ads popped up in their newsfeed. You can also use Google AdWords to get more views on your website.
Using a website called Fiverr, you can pay contractors from overseas to create posters, flyers, social media advertisements... the list goes on. These can be made within 24 hours and for as little as $5. I used this a lot. If making a poster, once you have the final copy you can have it printed and put it in a café (if you have permission)! This can be an easy and cheap way to get your name out there.
Above all of this, the best way to keep a busy business is to have a high client retention rate. Making sure clients do not fall off the back end of your business will help you to stay busy. Make a habit of asking your clients, monthly, if they are happy with the service you are giving them and if there is anything you can change to make them happier. Do not be afraid of their answer; it is far better than clients leaving you and not telling you why.