I also say that term of not keeping all eggs into one basket but in bitcoin, this is the opposite way. If you want to minimize your losses but to maximize profit, putting to bitcoin-only can be your choice. I have invested in other altcoins because it's my choice to diversify.
Bitcoin is a gem and if you have invested only into it, you have the best gem of them all. But as time passes by, you want to explore into altcoins and that's the start of knowing others of it through the researching.
For me I wanted to focus all the attention towards bitcoin for the main time. Altcoins is good while Bitcoin was on the top price, but while it's not yet taking a good productivity just let it grow all alone and gain a better profit. Research is helpful, just be patience in doing it together with the hardworks that you have in reaching your goals.
You can explore anytime you want if you think that you have sufficient bitcoin on your portfolio. But as I've said, as time passes by and you have spare money to invest and you are okay with it whether it lose or get into profit, as long as you get to learn more about it, it's fine.
I'm contented with the amount of bitcoin that I have right now but as usual, I want more and while waiting for it to add in quantity I just can't stop looking to the movement of altcoins and I understand that many of them can easily burn my money. As long as you know what you do and you're okay in choosing altcoins, invest what you are okay to lose.