Relaxation is equally important at this stage … So take my advice don’t do anything related to Studies. Better is you can sharpen your skills in sports or other extra-curricular activities in which you are interested.
If you really want to study then study the following-
C Language
AutoCAD
Rest of the subjects you can study only when you have the college books because those are followed and you ll have to study specific things from that only.
I can tell you the course structure of first year
1) Workshop
2) General Biology
3) Mathematics 1(vector algebra)
4) Thermodynamics
5) Electrical Science
6) Physics Lab