A good strategy is to sell coins that will go down first and buy them again when prices start to fall. This requires good planning and proper analysis of the coins that will fall, making a buyback at the lowest price will add to the coins you have.
Altcoin is the best in my opinion is to buy some ETH because the current price of ETH is around $ 114. ETH has a good future with technology that has always been developed by its developers. ETH is able to offset the price of bitcoin. I only recommend ETH, if you have another altcoin option, first make sure the coin has good technology with developers who are always active.
It wasn't just a good strategy that saved me. I follow the news, and when I found out the bad news about oil, I put out stop orders for sale. They worked almost immediately. Then I was lucky to guess at what price to buy the same number of coins. I certainly did not buy them at the lowest possible price, but it was much lower than it is now.
I am not in a hurry to buy altcoins, because I do not trust them as much as bitcoin and I already have a good profit, which would be stupid to lose by my hasty actions. So I'm still looking at altcoins. As for ETH, I no longer believe in this coin, it seems to me that the peak of its use has already passed. Speculators can certainly pump its price, but this will not bring ETH price above $ 300. There are much more promising coins in terms of large growth.