No,it is not good to buy other coins for bitcoin,if you really like bitcoin then you should buy bitcoin for now because we are still in the early days the prices will reach more high when compared to current price.So buy bitcoin how much you can because you can even buy small portion of bitcoin when the prices were around $7000.And one more don't buy bitcoin when the prices keeps increasing just buy it before the prices going to increase then only you can make money.
The situation does not remain the same, sometime the altcoins value are low when bitcoin value is low and sometimes both bitcoin and altcoins prices increases at same time. Buy when u see cheap prices.