Californians for Political Reform, a coalition of widely disparate groups led by anti-tax crusader Paul Gann, have begun gathering signatures statewide to qualify an initiative for the June, 1990, ballot that would strip the Legislature and governor of their reapportionment power. The measure would create a 12-member bipartisan citizens committee to redraw legislative, congressional and Board of Equalization district lines. "We think people are ready for significant reforms," said Bob Marks, spokesman for the group and an aide to the initiative's author, San Mateo County Supervisor Tom Huening. Redrawing district lines carries significant political impact because the majority party traditionally designs boundaries advantageous to its own candidates. The initiative is one of seven addressing reapportionment that are now in the pipeline.