I think your choice is correct by choosing bitcoin to invest in, but if you are looking for altcoins to invest in now are Ethereum, cardano, and Bnb. I think some of the altcoins that I mentioned will be able to benefit you if you hold them for a long time. ethereum promises more profit if you are able to hold it for a longer time.
What is clear is that what you mention is the top coin of all and for a long term investment it is very worth it,
especially at this time Bitcoin is in an uptrend which is also followed by altcoins,
In addition to the three altcoins you mentioned, I think there is another one that is good for long-term investments, namely Matic, which is a coin that has the potential to continue to grow
I do agree that there is a good chance we could end up with Matic doing better in the long run but there is an equal chance it may not do as well as we hoped it would. Doesn't mean that it will go down, but just not as good as we imagined. ETH gas fee is not as high as it used to be and people assumed that the only reason to use Matic would be to eliminate the costs of gas fee and instead use Matic.
However, as we can see right now, that doesn't seem to be the case. This is why I believe that there is a good potential, because if it is not high only due to eth gas fee, then it is a good sign, but why is it high? We do not know that now, we assumed it was due to eth gas fee but if it is not that, then what is it?