VOTE
In my opinion, the individual action that matters most is voting for public office and voting with consumer dollars. Climate change is a problem governments will solve, not individuals.
However, individuals can support the transition to a net zero society by voting in leaders that demonstrate strong action on climate mitigation and climate justice, as well as showing companies that sustainability and regeneration are values that matter to consumers in the lifecycle of goods.
Wear what you have
You do not have to buy anything new at all to practice sustainability in your own closet.