Dragon King's Unlikely Cousin

In the beast taming world a person's standing is set by the beast he contracts with, and a failed contract marks him as a washout. Spencer crosses over from the modern world and fails his. His girlfriend leaves him and joins the people laughing at him. What he wakes instead is a pay-to-win system, which turns money spent into strength. The black dragon he runs into turns out to be his cousin, who came over the same way he did. More of his relatives surface as SSS-tier dragons and he brings them in with him. Nobody can say why the family all came back as dragons. Spencer uses the system and the dragons to go after the people who wrote him off. He breaks the Shaw clan and puts down the wave of beasts coming out of the wild.