There are a lot of people who love coding but never find the right timing to start coding as an athlete in competitive programming competitions.
As someone who ranked 1344 internationally as a pre university student in a university students competition, HashCode and then ranked 545 internationally among participants worldwide in Google Code Jam Qualification Round, here are a few of my tips.
Start with :
30 Days of Code - https://www.hackerrank.com/domains/tutorials/30-days-of-code in a particular language
Choose that language from the Dashboard and solve as many problems as you can. https://www.hackerrank.com/dashboard [ Do it once in a while ]
move on to completing the Problem Solving ( both Algorithms and DS ): https://www.hackerrank.com/domains/algorithms
along with solving questions on Top Coder, CodeChef and LeetCode.
For specific topics, try Interview Preparation Kit: https://www.hackerrank.com/interview/interview-preparation-kit
Solely for Practicing Code:
Doing all of the above the righteous way would give you enough exposure and knowledge to be competing without being hopeless. Anyhow, wish you luck on your coding journey! :)