Stackin’ has raised $12.6 million in funding to expand its personalized text message platform aimed at helping young people save money and invest. The Los Angeles-based startup said the series B funding round was led by Octopus Ventures, and Marieke Christmann, principal at Octopus Ventures, will join the company’s board. New and existing investors included Experian Ventures, Cherry Tree Investments, Dig Ventures, Mucker Capital, Unlock Venture Partners, TechStars and Wavemaker Partners. Stackin’…