Hi,
I'm sorry to say this so directly, but you're not ready to start such a big project.
Here are some points that may explain my point.
- Referring to your latest works, you only know simple commands such as printing and using sprites. To start a big project, you need to understand a wide range of commands and have experience.
- According to your request, you're unable to get the graphics you need for the project. This will quickly stop you, and I'm not sure why I even need to tell why: nobody in this community has good sprite art skills. Even if someone proves me wrong, be aware that you will need a good reputation if you want others to work for you.