There is a lot of answers but if I'd say just one it would be rejecting the current institutional power. At least right now in our time period. Fully rejecting the imperial state, no matter how much they potentially benefit from it seems like a solid transition
we are all lib so let's not gatekeep what leftist™️ actually is. I guarantee you were a lib once too(still are, but once too.)
I agree though that having had some material resources before is a pre-condition to class consciousness of that sense. There are other forms of class consciousness like that of workers who never got beyond paycheck to paycheck in poverty - even in the imperial core - or that of agrarian workers in China in the last century, or indigenous resistance elsewhere.
But the labour aristocracy (which benefits from imperialism) in the core and of that the subsection which had "decent" lives (controlled by full work weeks dividing social relations between you and family, offspring and partners, controlling social relations to you and the community) those need to fall a bit to real change what they think and how they will act within the framework of a mass movement.
The funny thing is that during a transitional period in which money is still accepted and used the vital resources of material, social and mental capacities they can command with it could be used to strengthen our movement. My hot take is: It was good that Engels financed Marx and the party.