How Long Does It Take For Yasmin Tablet To Be Effective?

HI, i was just wondering,; how long will it take for yasmin to be effective?? . I started my period the 26th of septemeber. And then started yasmin the 9th of october. (i an taking Yasmin 21 +7 placebo). Do i need to wait until my next cycle for it to be effective?

Can i just skip the placebo pills and continue with newpack of white pills? Will it be effective as soon as i take the first pill of the new pack?