"Would like" always take "to-infinitives". You can say "I'd like to improve" or "I'd like to practice". You can also say "I like improving" or "I like practicing". Of course, "I'd like to" and "I like" means two different things. "I'd like to X" means "I haven't done X yet but I want to do X" while "I like Y" means "I already do Y and I enjoy doing Y". Hope this helped!