Here's the example of how I invest/trade: I've done a lot of research on 2 coins: ETH and NEU (Neufund). Both have solid use. My team uses Ethereum for software development so I follow closely it's network usage, and I know pretty well how many companies use it for various purposes. Neufund is the first Equity Token platform, it's economics are clear to grow and generate income, I follow it's channels closely and know what's happening. Besides these I also own Bitcoin for diversification and cashing out. Besides these that I know well and follow closely I do not buy any other coins, I only earn tokens of my clients through work. When any of my holdings get to gains of over 50% I start selling them slowly, to USDT or to other tokens if they did not grow as fast. For example I sold ETH for BTC when it reached 0.1. Then if the coins drop over 60% of the peak, I start buying them. I never sell on the downturn or buy after token is over 80% of it's historical high.
This indeed is a good strategy. My strategy are similar while buying with fiat.
I select a number of coins which I believe do have a future. I buy when they are going low or high and are below 50% of their peak value, I keep on buying the coin if it keeps decreasing in a decreasing amount while stops buying when it keeps increasing and I set 50% of the coins on sell order above x2 of my buying price hence bringing back my investment in any time in future.