Yeh for a decent profit in Cryptocurrency you should follow both things like buy small small amount at every dip and then hold it for long term which will be beneficial to raise you portfolio.
Currently price of Bitcoin is surrounding around 29k to 30k, later which will be definitely dump down to around 28k and the possible reason is to liquidate all long positions, so the point is that market provides opportunities to buy Bitcoin at cheap after several days, no doubt buying Bitcoin at any price will always be profitable for you because Bitcoin has a history to retest his ATH and make new one, but in order to get more profits you should go for DCA instead of buying big amount at any price, one things you should keep in mind before investment use such amount of money which you can ability to lose and also those amount which has no spending need in short period because some time Bitcoin took long to recover his price so your wait can be long too for a profit.