I personally studies ISCA from Manish Valecha... this books gives memory codes so that u can recall the answers easily in exam.... I suggest go for this buk...... I got 54 in this attempt...
For Cost I did Sanjay Agarwal videos + PM..... Do solve PM it helps alot........ Dont go for solving each and every question as it is not possible.... But atleast do one question from each topic.....