There are a lot of ways to grow business fast when you have money. Advertising is the biggest driver of growth with money.
There are few ways to grow business fast when you are on a small budget. The best one that generates results is out-of-the-box marketing. Meaning, doing something that has chances of going viral. I was reading today about a pizza owner that started asking people to give one-star review in exchange of discount. He did it out of frustration with Yelp Sales calls but the sign board went viral and gave him huge media coverage. It also boosted his business greatly. That said, viral marketing is often risky and can backfire. So, play it nicely and after much thought.
Building yourself as a brand online is also a great way to grow. Not a fast way but it must be part of your marketing strategy. Here's a blog to get you started!
https://www.upreports.com/blog/build-brand-identity-online-100-tips-ideas/