Which topics do i have to …

You should be thorough with the chapter naming of organic compounds first(If you know the names of organic compounds only you will understand the topics clearly as all topics of organic deals with some or the other ORGANIC COMPOUND.As you need to know the name of a person to address him).Then you need to move on to the chapter reaction mechanism which is the base chapter for class 12 (topics like resonance/mesomeric effect,inductive effect,hyperconjugation ,electromeric effect,substitution and elimination reactions and their mechanisms,reactions on benzene and some rules like markov nikov rule and anti markov rule).These topics mentioned are really important as these are the concepts you need to clarify first to get onto class 12th.Almost all the organic chapters of class 12 deals with one or the other topics mentioned above(mainly substitution and elimination reactions).So I think you should cover up all these portions first and of course read the ncert thoroughly and wish you all the best....

Inductive effect, mesomeric effect, GOC, Nomenclature, etc