Understand that they don't mean exactly the same thing. 'I like improving' means that I find pleasure in whatever improvement I've made (as I continue to practice) or that I might make in the future. 'I would like to improve' means that my goal (my objective, my desire) is to improve.
Similarly, 'I like practicing' means that I find the process of practicing enjoyable, whereas 'I'd like to practice' means that I want want to practice.