The two types of growth curves are exponential growth curves and logarithmic growth curves. In an exponential growth curve, the slope increases more and more as time goes on. In a logarithmic growth curve, the slope increases sharply and, over time, the slope decreases until it becomes flat. Understand the type of curve you are facing so that you can set your expectations properly.
And if you're not happy with the type of growth curve you're on, start playing a game with a different curve. Once you understand the type of growth curve you're facing, there are two ways to accelerate your progress on a given curve.