I find that it is very dangerous when you buy crypto under the top 100, because those cryptos will not be guaranteed by the crypto in the top 100. so I think you should buy cryptos that in the top 100, beside Bitcoin there is a lot of potential cryptos.
Many of the coins in the top 100 give not a guarantee either that you are going to get profits, in fact if you check out the coins that were at the top of the market a few years ago you will find that most of them have disappeared that is why the only coin that I am sure is going to be here for a long time and that I am willing to hold is bitcoin, every other coin is a coin in which I do not trust as much as I trust in bitcoin.
I think it is a correct time to buy anything, weather that is bitcoin or any other coin as long as the coin is not a scam coin than you will be fine. I personally put most of my money on bitcoin and ethereum and I have put aside a smaller number on some small coins like nano and spectrecoin but I did not put too much on them I just have enough to say they will make me decent size of return if they go back up again.
My main bets are bitcoin and ethereum right now, I believe both can really go x2 soon, maybe not right away but I am definitely expecting a bull right about these days. Other smaller ones I bet small but I expect them to be like x10 increase when the bull comes so that is why I can live with smaller investment for them since the return would be still big if it goes up like I imagine.