The electors shall have the power to approve or reject at the polls any ordinance or resolution passed by the Council, except as hereinafter provided. Only electors of the City may circulate referendum petitions. Within thirty (30) days after the passage by the Council of such ordinance or resolution or its repassage over the Mayor's veto, whichever is later, a petition signed by at least ten percent (10%) of the electors of the City may be filed with the Clerk of the Council, requesting that such ordinance or resolution be either repealed or submitted to a vote of the electors. If said petition is signed by twenty percent (20%) or more of such electors, the date of the election may be fixed therein, not less than ninety (90) days from the time of filing thereof. When such petition is filed, the Clerk shall first ascertain the sufficiency of the petition, and if found sufficient, the Council shall thereupon, within thirty (30) days of the filing of such petition, reconsider such ordinance or resolution. If upon such reconsideration the ordinance or resolution is not repealed, the Council shall provide for submitting it to a vote of the electors on the date so fixed, or, if not so fixed, at the first general election in any year occurring more than ninety (90) days from the filing of such petition. No such ordinance or resolution shall go into effect until approved by a majority of those voting thereon, in which event such ordinance or resolution shall go into effect on the fifth day after the day on which the Board of Elections certifies the official vote thereon. When the Council by general law or under provisions of general ordinance is required to pass more than one ordinance or resolution necessary to make and pay for any public improvement, the referendum provision shall apply only to the first ordinance or resolution required to be passed and not to any subsequent ordinances or resolution relating thereto.