Here are some of the important books you can prefer for GATE Mathematics.

• Higher Engineering Mathematics by B.S.Grewal

• Engineering Mathematics - Erwin Kreyszig

Other books you can also prefer:

Linear Algebra : A.R. Vasistha (Krishna Series)

Complex Variable : J.N. Sharma (Krishna Series)

Calculus : A.R. Vasistha, Dr. S.K Sharma (Krishna Series)

Calculus : Shanti Narayan (S. Chand)

Vector Calculus : A.R. Vasistha (Krishna Series)

Differential equations: M. D. Raisinghania (S chand)

Complex variables: J.N. Sharma (Krishna Series)

Probability and Statistics : S.C. Gupta and V.K.Kapoor(S chand)

Numerical Method : S.S. Sastry (4th edition)

Graph Theory : Purna chandra Biswal(PHI publication)

Combinatorics : Purna chandra Biswal(PHI publication)

Mathematical Logic: Purna chandra Biswal(PHI publication)

Set Theory & Algebra: Rajendra Akerkar,Rupali Akerkar

For the information about GATE you can go through with given belwo link.

GATE 2018

Good Luck!