IMHO, the best stack is the one you are most familiar with. Start with what you are most comfortable with and build from there.

The hardest part is coming up with a product that someone else would pay money for and then making that first sale.

btw, I love reading about tech stacks, This vs. That vs. Other blogs/articles - but honestly, it just a distracting hobby at best.

This is advice for bootstrapping. If you're trying to get a job, then yeah, focus on some specific stack and start learning it and building projects to put on github and blog about.