What amount of liquid capital would you deem appropriate to have before beginning to "invest" and not play with stocks? I have heard that it is not worth the ri

What amount of liquid capital would you deem appropriate to have before beginning to "invest" and not play with stocks? I have heard that it is not worth the risk for anything below $18,000. Same question, only for options. What percentages of capital should someone in their 20s split investment between bonds/index funds/stocks? What do you think about ishares vs. ETFs for 8 months to 2 year investments into emerging markets?