Isaac Hayden, a £3.5m buy from Arsenal, opened the scoring in the 20th minute as he swivelled to hammer home a low right-foot shot after Ritchie’s free-kick had been blocked.
There had been controversy within three minutes when Gayle used his hand to guide an Ayoze Perez cross past Ali Al-Habsi and into the net.
Referee Andy Madley initially awarded the goal but while Gayle celebrated, Reading surrounded linesman Paul Hodskinson.
The goal was ruled out and the Toon striker deservedly booked.
But Jaap Stam’s Royals looked overwhelmed early on with Perez firing wide at the near post, Clark missing the target with a free header and Gouffran volleying straight at Al-Habsi.
Reading gradually gained a foothold and ended the first half on top.
Roy Beerens was unlucky to see his curler hit the bar while nobody was on hand to pounce after keeper Matz Sels had spilled a Danny Williams effort.
But after Al-Habsi brilliantly denied Gayle, he could do nothing about his thunderous setpiece and was also beaten at the death when the ex-Crystal Palace hitman converted a cross from Hayden from close range.