Thanks, Shiva Prakash — I suggest a combination of a) Acquiring mathematical knowledge systematically and b) Regularly practice in applying that knowledge to solve interesting problems.

For a), try Khan Academy — lucid explanations and lessons are delivered in sequence. But also seek out other lessons as no single exlanation is guaranteed to make sense. For b), check out resources like YouCubed and Nrich. The key is to pursue a) and b) in parallel.