Hello, I wanted to ask if I should just buy BTC/LTC/ETH right away when I get the money, or should I wait a couple of weeks to see if their prices go down?

I recently started bitcoining, and I wanted to get more bitcoin by waiting for it to go down, since it did go down a lot last month, I thought it would do it again, but it didn't instead it went up.

So, I wanted to ask if I should just buy the coins when I get the money or should I wait for a couple of weeks or so just to see if their prices would go down?