Hey,

It depends on you, which subject you are going to choose in GATE life sciences exam. As per my knowledge, you have to read two books of Pathfinder Publication for developing your fundamental concepts.

Life Sciences Fundamentals Practice I - Pranav Kumar, Usha Mina

Life Sciences Fundamentals Practice II - Pranav Kumar, Usha Mina

After developing concept, you must practice Questions from MCQs of Pathfinder Publication

For Chemistry part, you can read 10+2 level of NCERT books.

Hope this helps.