JEE

First thoroughly go through ncert at least for chemistry and physics.
After this go on through HCV(physics) and Irodov(physics).
For chemistry the study material in ncert is more than sufficient for jee mains but for advanced you can check out specialist publishers in organics and inorganic and physical.I recommend u Morrison or OP Tondon for organic.JD Lee for inorganic and RC Mukherjee for physical.
For mathematics NCERT is not sufficient. You have to upgrade your skills particularly being engineering aspirant.
So you should purchase a series of mathematics books from the same publisher eg CENGAGE or ARIHANT
You have just to be focused on whatever you are aiming for. And finally I will recommend you to buy a regular test series package from any of a reputed institute eg Resonance or FIITJEE to test your learning skills at regular interval.
Good Luck

I will suggedt that you drop a year and prepare for competitive exams again. Devoting one full year for competitive exam preparation has its own merits and demerits. Dropping a year means that you will get sufficient amount of time to prepare for competitive exams. It will allow you take mock up test and help to score good ranking in competitive exams. However, one year is a long time so the possibility of you may change your goals and objectives. You may become lethargic because of availability of time and lesser pressure. You may waste time. If you are confident of keeping the momentum, dedication, determination, readiness to work on a plan, will to achieve your objective and support of family; you may consider dropping a year for competitive exams. It is worth try option.