200 is not too difficult in JEE Main.
U just need to clarify your concepts. .200 means approximately 66 in each subject. Hardwork and clear concept are enough for this.
The key to success in MATHS is practice. The more you get it, the better you practice. The questions asked in jee mains are not very high level. If you have practiced enough, you can get the amount correctly and quickly. Effective to me, it is a game changer in exams and of course if u practice u can expect a lot more than 66 marks (around 100)
In CHEMISTRY you need to be very clever. Questions are asked from Organic Chemistry, so make sure if you are a Concept Blast. There is a lot to mug there and with constant practice it will become much easier. Theoretical chapters should be studied with NCERT, which will suffice. If you find similar chapters like chapters difficult, try moving easy chapters from there to focus. This is considered by many to be the easiest part, so make sure you are well prepared.
PHYSICS is something that many candidates find difficult and try to take it off. But it will be easy if the early chapters like work force, friction, center of mass, surface tension and rigid body mechanics are obvious to you, then you are very difficult to begin with, but stick with it and you take time. Be suspicious of all of you. It is clear about these chapters that it will not be too difficult. The key concept is important. Practice good books like HC VERMA and it will be enough. Get more than 85 marks (try dimensional analysis when you cannot solve the question. Try to check that it is dimensioned with options that can give you the answer)
Try to aim for 250-300, you can be a little less than the target but still be above 200