Firstly I'm glad that you have decided to take a drop ans it requires courage and self-confidence to do that. 

If you are preparing by self then I would recommend you to buy DLP course of any good coaching institute. 

As DLP courses have certain advantages, like

• Your material would be in line with the JEE mains/advanced standards. Also would not be reuiriing to buy any other book or material
• Mostly the dlp material is completely solved so it provides an added advantage.
• Also DLP courses provide test series which is an indespensible resourse for the preparation of JEE.

Now regarding understading the materail, I would recommend you to rely on YouTube

Channels like Mr. AA - MNNIT Allahabad, Sachin Rana - IITB etc are the few to name channels which privides quality video lectures in the JEE domain. I can bet you can cover 70-80% of the JEE syllabus from the resources and which is more than enough for cracking a decent IIT (also this line holds for  a eneral category too)

All the best for your fantastic year to come ahead..