You will need atleast 600 for a seat in GMC in Delhi even with OBC reservation under State Quota. This is because in 2019, under State Quota, a score of 567 secured a seat in Lady Hardinge Medical College under OBC Category. That was the cut off. Now this iis 2019 data and cut offs change every year. Cut offs change every year depending on various factors such as no.of Candidates appearing for the exam, no.of Candidates qualified, top NEET score and difficulty of the exam. So you will need atleast 600.If you are appearing for NEET 2020, this might help you:
This year, along with your Admit Card and Valid Id proof, you should also carry your Mask, Head gear, gloves and a sanitiser to be careful. Also take an passport size photographs along with your admit card. NTA released the following protocols:

Contact less frisking will be ensured.

Time slots will be staggered for Reporting to the exam

Contact less verification of documents

Candidates will have to carry a self declaration regarding their Corona free health status

Candidates with more than required body temperature will be allowed to take the exam in isolated rooms

And then you need to report to the exam hall atleast an hour before the exam for checking. And then regarding the dress code, either for girls or boys, it needs to be simple with no big buttons or embroidery or metal chains hanging. No jewelry of whatsoever metal will be allowed. And no watches or electronic gadgets will be allowed. Simple sandals are allowed but not shoes.