My first strategy was simply productivity. I put out on average a book every two weeks. Due to market saturation though this is no longer recommended. My advice now would be to know your market, design the book accordingly, and make everything as professional as possible. This includes optimizing keywords (fiverr is great for SEO work) and then using those keywords as starting points for Amazon ads- which are now unfortunately necessary to even rank anymore. Regardless of your strategy, you need to always experiment and engage- there is no set it and forget it approach.