Start with NCERT books of all the three subjects to clear fumdamentals.

For Organic chemistry follow-Arihant, Morison & Boyd, Finar vol. I.

MTG publications PCMB gives papers from various exams which is quite helpful.

Whatever coaching class you join, attend regularly, attend all tests, get your doubts cleared from your teachers; experts on this site are also available to help you.

Follow a regular schedule for studies and also regular outdoor exercise,yoga, meditation/pranayam  all together atleast for one hour.Eat healthy food, avoid fast food which makes us lazy.Take good sleep for six hours.

Have faith in your efforts. Best wishes.