What else to invest beside real estate rental

[Lisa Forde]

Hi all, Once you have enough property on rental and you think that's all, you need to diversify your investment portfolio, but you have no experience on stock or mutual fund or EFT, you just hear them. what would you do when you first investing something else besides real estate. buy a SP 500? vanguard? just curious if you guys all invest on real estate or you do something on the side. thanks