Does anyone know a universal recipe for determining the prospect coins, which in the future can be earned? Does it make sense to buy this coin?
There is never going to be a "universal recipe" about anything. Crypto is a gamble.
However I can say privacy-focused coins are gaining momentum lately. You can have a look at the current prices of some of the privacy-focused coins below and have your own judgment for Bitcoin Private:
DASH: $1240
Monero [XMR]: $394
ZCash [ZEC]: $586
Some of the previous Bitcoin forks have also been popular, even without any privacy features:
Bcash [BCH]: $2400
Bitcoin Gold [BTG]: $270