The three main factors to consider for diversification in investing are time, asset allocation, and equity spread. Time refers to investing a certain amount at specific intervals to avoid emotional investing and reduce the chances of picking the wrong point of entry.
Asset allocation means that you invest in a mix of high-risk and low-risk assets in a proportion that complements your risk tolerance and investor preferences. Equity spread means that you have a suitable number of stocks in your portfolio. Three or four is not enough unless they are diversified ETFs with numerous stocks.