40% Invesco QQQ Trust (QQQ), this is stocks.
40% iShares 20+ Year Treasury Bond ETF (TLT), this is bond.
20% SPDR Gold Shares (GLD), this is gold.
I have done backtesting many times on portfoliovisualizer.com, and from Jan 2005 to Sep 2018, the annual return is over 10%, and the max drawdown is 16%, compared with SPY, the annual return is about 8.7% and the max drawdown is about 51%.
The period inludes the 2008 financial crisis, and too many people had huge losses at that time.
You can check this backtesting image from portfoliovisualizer.com.
You just split your money according to the portfolio percentages, and balance them every several months.
Here is my recommendation for investing, focus on your job and make money regularly, then save money to do investing according to the portfolio suggestion, and you can be rich and retire earlier than you can imagine.