Since Bitcoin is said to be the costliest of all in the crypto market the fluctuation in its price affects other coins
this is to say when the bitcoin price drops, every other coin drops in their market price so drastically that will be noticed easily making them attractive to buy following the fall
this method will enable one to gain more coins than expected, following the records most of these coins have gone high in time past when the bitcoin price went up so buying more when the price falls seems to be a great trick on acquiring much more coin than expected, this is to say the fall enables us to use less fiat to acquire more coins
will you advice other users to purchase weaker coins when the bitcoin price drops or buy the bitcoin itself?
I am not buying when price drops in the start of the bear run, because it can still drop -%70 and another -%90 after that. I rather look for signs in the market when coins with similar level of market cap are getting signs of life again.
Also i would seriously never advice anyone (at least my fiends) buying "weaker" coins, or altcoins in general.
If i see something that i believe to have strong future, i still not "advice" buying it. At least not anymore and not my friends. If the person who asks my advice is a friend, i just say what i am seeing in charts, and what i am putting my money in and how much. I will however say that they should only expect to lose all their money.