For a secure investment it is important to have a well diversified portfolio,
with a good weighting of the different assets, you will be able to achieve a return that is more than correct and secure.
Nevertheless, it can be interesting sometimes, with part of its capital, to take a little more risk, although still mastered, and invest on individual values when one has a strong bullish conviction.
A rather reliable method is to use the 200-day moving average as a benchmark.
This technique was mentioned in the book Money, master the game of Tony Robbins, it is used in particular by Paul Tudor Jones, one of the largest trader and hedge fund manager.
To summarize, the principle is to be positioned only when the price is above this moving average (5% is a good entry point to avoid false signals), and conversely to cut its position when the price passes underneath (5% below is a good benchmark too).
Using with ETF SPY