As we covered many times, that is not the only question. The other important factor is how many BTC you already have... I have always said if you don't have any bitcoin, you better get started right away, and the price does not matter, since the ONLY way to prepare for UP is to buy some.. otherwise you are ONLY prepared for down, which, generally speaking, is not a good place to be.
Getting started as soon as possible should be the only thing that one should be thinking to do next, but the interesting part is that not every one wants to get involved into Bitcoin because of the misconceptions that they have.
However, it is true that not everyone has a fear on Bitcoin that Bitcoin will crash and their money will be all gone and not come back again.
Although, one thing that I believe for sure is that as long as Bitcoin is fluctuating, it will drop and it will still skyrocket again, so what I am trying to say is that, even if Bitcoin drop now it will still rise again and as Bitcoin is dropping, it is also given some others who are yet to because an investor a chance to buy as much as they can and hold it for dear life.
So the question for each person has to do with their own assessment regarding if they are sufficiently prepared for UP or not, and if they have $10k in an investment portfolio, and they are happy having $1k in BTC (which is 10%), then that is their choice, and maybe 10% is enough. I generally recommend that beginners have anywhere between 1% and 25% in bitcoin, so the details in regards to where they fall and if they have enough still is within their discretion.
Moreover, everyone have a choice to make, but the greatest choice that they should make is to make sure that they are holding on to something that worth holding, there are many people that are holding something that doesn't worth holding (shitcoins and the rest of them).
But as many that hold Bitcoin, 15% of 100% that they make during the week or month from what they are doing should be put into Bitcoin so that they can accumulate as much as possible that they can afford.
Although, it really depends on the amount of expenses that they do during the month, some expenses will make one not to put up to 15% into Bitcoin and some will put more than the 15% in Bitcoin weekly or monthly.
When you withdraw your bitcoin, you need to consider the future transaction fees and not just the current transaction fees, and lightning network is not a great place to store for the long term, but it is good if you want to conduct a bunch of small transactions. If you have a choice, I don't think that it is good to have your UTXOs to be smaller than $500, even if you might end up holding some of your money on exchanges longer than you otherwise would have. The guys who sent multiple small transactions to the same wallet are likely going to be in BIG trouble when they go to spend those transactions, especially if they want to do a larger transaction that has to combine several prior transactions (UTXOs). They might end up losing a lot of money on their bitcoin and/or not being in profits as great as they thought that they were... think about $5k in bitcoin that had been built based on 100 $50 bitcoin transactions, and then if you go to spend it, the fee is going to be 100x more than if the transaction had been in one UTXO.. .so maybe it could cost up to $2,500 to send it.. or if you figure out a way to reduce your transaction fees.. maybe you get it down to $500 for the transaction fees because you are combining 100 UTXOs that were $50 each.
Transaction fees can sometimes be the problem for some investors that are skeptical, but as for me I will likely say that it will be good for one to not think about the transaction fees and keep on investing every now and then as long as the money to invest is coming.