1the main thing is building of concept, the so called "easy" books sl loney and hall & knight have not been written by their authors for the purpose of iit jee preperation, they provide a solid foundation for building your concepts.....
if you have found something very "tough" it means that you have not sat with the problem long enough or got scared by just looking at the problem because according to me a "tough" problem is a combination of several "easy" problems.....as it is usually the case in iit-jee
so as far as maths is concerned, you have to sit with problems a bit longer and then u will finally feel that everything is "easy"
i would always recommend that u choose 1 or at the most 2 books for any topic and practice sums of that topic from that book only rather than using several books and getting confused