These guys are all talking about how to best shield any earnings from tax gains. Once you figure out which account to place what’s currently cash, the next step is what to invest it in.

I keep my money in a fund called “FFNOX”, which is a simple 85% equity 15% bonds fund that’s well diversified. Fidelity also has “target date funds” that rebalance differently according when you plan to retire–they target 2040, 2045, etc, and slowly shift the allocation to bonds from equities to lower risk at target date. Finding one with a low expense ratio (amount you pay per year per dollar for their management) would be the simplest way to go. Since you’re with Fidelity, their Freedom target date funds seem cheap enough.