The following given below are the mark vs. rank predictions of the year 2018:

Marks 140 < Rank 100

>130 <300
>120 <600
>110 <1200
>100 <2000
>90 <3200
>80 <6000

I hope you can get a clearer idea through this ranking. We'd advice you to complete the NCERT books for 11th and 12th first. Along with that, try to solve mock question papers.

For Math, If you have a good grasp of calculus and coordinate geometry you should be able to achieve this score.Vectors and 3D geometry are the most important topics in algebra part so prepare them well. For Physics, optics, mechanics, electrostatics would be a good place to start off with.For Chemistry, focus on the exception questions, as these are very common in WBJEE. 

All the very best!