Hello Dear,

There are few chapters in which you can focus on few chapters:

Physics:

these are the chapter where allen doesn't provide good stuff. They are mentioned as following.

Class 11:

1. Work power energy(sheet)
2. Wave and sound

Fluid(Actually no one is perfect in this chapter)

Class 12:

Topics related to jee mains

1. Earth magnetism
2. Magnet
3. Optical instrument
4. Semiconductor

Maths:

these are the chapter where allen doesn't provide good stuff. They are mentioned as following.

Class 11:

1. Trigonometry (some easy stuff is not there)
2. Quadratic (same as trigonometry)

Class 12:

Does not seem to be anything.

Chemistry:

these are the chapter where allen doesn't provide good stuff. They are mentioned as following.

Class 11:

1. Redox reaction.
2. Some portion of chemical bonding.

Class 12:

1. Thermodynamics
2. Last few chapter of NCERT

Good Luck