There are too many factors to consider before you deciding to invest in crypto and there's a basic rule but it doesn't mean that's is easy to perform.  The main rule could be to buy when the price is low and sell when the price is high, but your question is when it will happen.

Actually, the price of cryptocurrencies especially Bitcoin isn't easy to predict or it's unpredictable.  So, let's have our own technical analysis or even fundamental analysis, to have a guide to predict the market even though you can't assure it is accurate but at least you have a source of predicting the market.

My suggestion is the same as yours, always head up into top coins in the market cap, they had potential upon holding in long term but not in a short period of time.  Plus, if you can focus on Bitcoin much better, for the safe-haven investment that is a good choice.