Don't try to buy an asset at one price with one lot, in most cases you won't guess. ETH is definitely a good asset for long-term investments, so you can buy it anytime you have free money, or on corrections. That is, you can buy some ETH right now at the current price, if it goes down, you can buy more, and if it starts to go up, you'll start to make a profit.

Many people think that they can buy with all money they have once and then it will grow, but in 99% of cases they don't guess. So buy in batches and average your average purchase price.