I don't feel there is some right rating to start learning. Start learning right now. If you are a real beginner, start with sorting techniques and greedy algorithms. Also, learn basic graph techniques like BFS and DFS.

Say you get a graph problem. Here, the question will basically ask you a variant of BFS or DFS which can solve the problem. All you have to do is understand the problem and make the necessary additions. You will get a hang of it once you start solving problems.