How do you defend what you're building from those who have more resources than you?
More like how do you prevent outside influences from reinstalling the previous government? History has shown that wealthy elites will help each other collectively maintain power.
What does the government look like?
This really depends on how bloodless this revolution is. If it's extremely bloody we may just see a less ludicrous version of the Taliban's government post US-exit. Where the new government lacks individuals with authentic public service experience.
Would you keep anything from the old systems?
The old systems will likely come back if not replaced with something better.
What kind of leaders would you need?
Not the ones calling for this crayon consumer rhetoric. You'd need people who have both experience and community ties. The people calling for violent revolution have neither of those.
How do you stop it from turning into the NEXT horrible thing?
You can't post-revolution. The inevitable outcome will be determined by how the revolution is achieved.