NJ.com – Online gambling’s slow start in New Jersey, the most-populous U.S. state to legalize Internet bets, has casinos reassessing their marketing to would-be players. Boyd Gaming Corp., the leader through its Borgata Hotel Casino & Spa-related websites, is reducing advertising after reporting a $3.2 million loss from the business in the first quarter. 888 Holdings Plc, which operates the US.888.com site, is shifting its advertising focus to slot machines from poker. “We are absolutely shocked by the slowness of the market,” Brian Mattingley, chief executive officer of London- based 888, said in a telephone interview. Revenue is coming in…