My advice is: try to hold as many Bitcoins as possible.
This is probably a good advice.
(assuming you won't buy if you can't afford to lose)If you are not rich, you also need to hold at least one Bitcoin.
This, on the other hand, is a nonsensical advice. First off, what does it mean “If you're not rich”? If you don't have a million dollars? A billion? If you don't own currently $43,217.80? That you're an average Joe? Lots of people consider that one Bitcoin worths lots of money today. If they're not rich, how can they accumulate it?
Secondly, why exactly one Bitcoin? These 100,000,000 satoshis aren't going to make you as rich. At least not as much as you may think. It is just affecting you psychologically that 1 of the 21,000,000 BTC
(which aren't tangible to somehow affect you, but anyway) will be owned by you. Would it be more appealing if I said that 100,000,000 of the total 2,100,000,000,000,000 sats will be owned by me? Nah.