Gratin founder Talal Abillama is a diamond in this era’s rough. Despite market conditions , his New York gallery keeps expanding. Some have attributed the dealer’s success to his wealthy family. Gratin’s artists say it’s something more. Starting May 15, “Blinds and Shutters,” the debut U.S. solo show by rising Spanish sculptor Mónica Mays , will greet guests at the raw Tribeca gallery that Gratin just leased for 10 years.  Although the space is barely bigger than Gratin’s current Chinatown home, Abillama plans to make Mays the 12th artist on its growing roster. “Hopefully, I mean, depending on how I do my job,” he told me over the phone, “because the sculptures are still being made as we speak.” Talal Abillama. Courtesy of Gratin. No. 15 White Street will be Gratin’s third location since it first opened at 76 Avenue B in 2022. Gratin only stopped renting that space earlier this year—even though it took over the former Grand Street home of storied gallery 47 Canal in 2024.…