Need guidance on how to start contributing

Hello I am new to open Source. I have been using django for web development for over a year and now I am very keenly interested to contribute in it. I am not sure on how to start contributing. I have read this https://docs.djangoproject.com/en/dev/internals/contributing/ and I have also implemented this dummy patch https://docs.djangoproject.com/en/dev/intro/contributing/ to start. I just want help on what tickets/issues a beginner can start with and how can I understand the code base better.