Led by H. Wayne Huizenga, the billionaire who has already made two fortunes, Republic is in the middle of an extraordinary buying and building binge. The company is following much the same formula that Mr. Huizenga pursued in consolidating first the garbage hauling business as the head of Waste Management Inc. and then the video rental business through the Blockbuster Entertainment Corporation, which he sold to Viacom in 1994 for more than $7 billion.