Yes, you could do networking later.
First design the structure of everything.
Have a decent layer of abstraction so that once your ready you can mold it any way you need it.
- Entities/components system.
- Game map structure
- Input handling
Don't focus on little details until down the line.
Everything will be ugly at first, but once you get a solid core perfected you can start adding in things to prettify it all up.
It will take a VERY long time. So don't rush it.
Take regular breaks to clear you mind, else you will grow to hate your project.