Computer case with good airflow, cable management under Rs. 7000 (Must be available in India)

Solution
The 690III is a solid case with 2 fans that provide plenty of airflow and has more than enough space for cablemanagement and watercooling setups.
a solid case for 50 USD is the Rosewill Challenger. While Rosewill's other products are... lackluster to say the least, the case has won multiple rewards and has the most reviews on Newegg out of any other case. It has okay cable management, comes with 3 fans, and is an all-around solid case, I usually recommend it to friends with their first builds in mind. Not the best case, but certainly not the worst.