You can look at what our ancestors did. It took voting against the lesser evil to end slavery. The Republican Party was a third party that abolitionists put forward after generations of effort failed to work either of the existing parties from within. In the end it took forming an entirely new party to actually push forward with abolition.

Grass roots party funded by the people and truly for us. Because big money isn't going to allow anyone to fundamentally change the system. Elect independent individuals into local and state governments as well who will work to remove first past the post and put in ranked choice voting. Again, expecting any of the big money parties to make change is the definition of insanity.