If it's in your budget, then I would try to hit the maximums for the 401k and IRA. You can invest in index funds within an IRA, although the 401k options may be more limited. I would say using tax advantaged accounts is even more critical if you're trying to retire early, and it's great that you're starting early to maximize the time spent in market. You might also check out r/FIRE for more early retirement planning.