I've split mine 4 ways, SP500, International, Mid-Cap & Small Cap. It's up to you. But I made my biggest holding the international at around 35%, Did SP500 for 30%, Small Cap at 20% and Mid Cap the remaining 15%. I like having exposure International and to smaller companies (I see the fees are higher but I like having the diversification even if the fees are somewhat higher), adjust accordingly if you have different preferences. Just stay with the low fee index funds.