If you want the correct guidance,kindly tell how low is your score. For good student even 90 pecentile is low because they have less chance to get a call from IIM.As your Past academic qualifications are average, and by assuming different scenarios, I would give my suggestions 

if percentile is 80-90 then you might get some good B-school,which you can see in the link below:

https://bschool.careers360.com/articles/what-if-my-cat-percentile-between-80-and-90-do-i-have-any-chance-at-top-b-schools

if percentile is 70-80 then you can get some decent B-school,which you can see in the link below:

https://bschool.careers360.com/articles/what-are-my-mba-admission-chances-70-80-percentile-in-cat

if percentile is 60-70 then you can get average B-school in this range,but my recommendation would be to appear for CAT 2019,as the Masters is very crucial,and most probably it will be your life's last degree, and your job and career will depend on this. If you doesn't want to drop a year,the colleges which accepts this range of percentile can be seen in the link below:

https://bschool.careers360.com/articles/where-can-i-apply-60-percentile-in-cat