If that $2,500 is just your spare money then you are good to go with any of it depending on what's your crave and you know after conducting a research.
Basically with these questions I don't have to think about it as I'm about to say most of the time to invest and buy bitcoin. You don't have to think about it if you still don't have bitcoin but if you are an altcoin fan and you don't have a taste of bitcoin, why not take eth first?
if we want future profits in a certain way, it's better for us to invest in bitcoin, because bitcoin is the standard for all altcoins.
Altcoin's future will always be different from Bitcoin, whose presence can still be lost from circulation because it cannot meet the minimum purchase target.
so investing in bitcoin is the safest and most profitable in the future.