Hey Roopa

Well it is difficult to precisely say anything about 2018 admission trend since a lot of it depends upon the difficulty level of exam, number of aspirants, their preparation levels, etc.

However, you may get an idea of the same with previous year statistics. If we were to see 2017 trends, then with a score of 2017, you could have gotten through most of the government medical colleges of Tamil Nadu with a score of 450. As per last year cutoff scores (i.e. lowest mark to get admission under Open category of Government medical colleges), a mark of 450 could have fetched you following colleges,

ESI-PGIMSR, ESI Hospital, KK Nagar, Chennai

Kanyakumari Government Medical College, Asaripallam

Coimbatore Medical College, Coimbatore

Government Dharmapuri Medical College, Dharmapuri

Government Vellore Medical College, Vellore

Thoothukudi Medical College, Thoothukudi

Mohan Kumaramangalam Medical College, Salem

K.A.P. Viswanatham G.M.C., Tiruchirapalli

Tirunelveli Medical College, Tirunelveli

Thanjavur Medical College, Thanjavur

Madurai Medical College, Madurai

Kilpauk Medical College, Chennai

Chengalpattu Medical College, Chengalpattu

Government Medical College & ESIC Hospital, Coimbatore

Government Medical College, Omandurar

Government Villupuram Medical College, Villupuram

I hope it will help.
Wish you all the best for your preparations.