This is not a good strategy at all because it doesn't work in a bear market.
This would work in either a bull market or a sideways market but if you kept buying whenever some altcoin made a new low, they you would be at a huge loss and would never recover since some coins are 90% loss from the ATHs.
And you can only sell the coin if you are at a profit, however what do you do if you are at a loss? Sell it when it rises at a loss and try and buy back cheaper? What if you end up buying it and it kept going even lower. This is not a good investment strategy at all.