It is based on your goals. Here are some scenarios:
- If you don't have a programming background and want to start programming quickly, it's recommended to start with Python.
- If your goal is to help AP Computer Science A course, you can start learning Java.
- If you have long term plans for USACO, C++ is recommended. In USACO Silver and above contests, some problems are not solvable with Python in the given time limits. Starting medium/hard USACO Gold problems, C++ have some advantages over Java.