Hello Harshida, If you are looking for taking admission in M.E/M.Tech/M.Arch programs, then yes you need to have a valid GATE score in order to be considered for eligibility. You won't be able to apply for PGCAT if you don't have a GATE score. Other courses like MCA and MBA don't require GATE exam.

Thanks for your query. It
is fine if you appear for Karnataka
PGCET 2018 alone. You would not require GATE scores to get
admissions to full-time MBA programme in Government and Private
institutes in Karnataka. The Karnataka PGCET MBA merit list is
prepared on the basis of marks secured by the candidates in the PGCET
exam. The marks obtained in the qualifying/entrance exam is
considered only for eligibility.

So do not worry!