Hey Rishika ,

U must revise first u r pre board paper and analyse your mistakes and go for test series of u can... okay..Now talking about sample paper u must take sample papers of DK Goel And TS Grewal For Accounts.

For economics must buy a ecovisionaire book and Together with sample papers.

For business studies  APC And Arihant or u can buy GS Aalag sample papers that are amazing. Now for maths u must be practiced from day one... And revised all formula , u r notes and all... Best book is RD sharma. And for sample paper ML Aggarwal.. sample papers.

Now for English buy  All in one English core  sample paper books and together with sample paper...First of all foe maths revised ncert first for two to three Times u must know each and every question of it ...

All the best!!