I think if he choos a low volatility slots, $100 wagering isn't that hard. It means he just need to wager a total of $100 and is not necessary to deplete $100 bankroll. Betting on Dice may probably needs $15 to fulfill that $100 wagering at a 98% chance of winning, maybe a little less on Plinko.
Calculating with that statistics, I believe it is worth a try to get 50 free spins since at a minimum bet it cost $10 plus the potential to win bigger amount.
The eligible games that qualify for the $100 wager requirement is limited to some games as quoted below:
Eligible games
BGaming: Four Lucky Clover, Mechanical Clover, Lucky Oak, Bonanza Billion, Gangsterz
Pragmatic Play: Clover Gold, Wild Wild Riches, Gold Party, Rainbow Gold, Wild Wild Riches Megaways
Spinomenal: Irish Treasures Leprechauns Fortune, Irish Treasures, Irish Lucky Dice Dice, Book Of Irish Treasures
It means that betting on dice and plinko is not counted, even if you wager $1,000, you will not get the 50 free spins. This offer is also limited to those who received the email, so anyone who are interested to participate need to check their inbox first. I received this email as well but I'm not going to take this offer because I'm not really familiar with all the selected games for the $100 wager requirement.