Hi Anikoli,
For the quant section,
MGMAT guides are good enough and they cover most of the concepts. The key point to note is you need to know the application of the concepts in the problems.
Complete the OG 13th edition and then also complete the Quant Review 2nd edition which is provided by the GMAC. Message me in case you want the Quant Review Book.
Coming to the Verbal section,
MGMAT SC is very good. I feel that is good enough. You need not be a grammar expert to crack the SC. Just make sure the meaning of the sentence is not distorted when you apply the error types to get your answer.
For CR, i recommend that you use Power score, OG 13th edition and Verbal Review 2nd edition
For RC, I recommend that you practice reading(maybe journals, novels and newspapers). OG 13th edition and the Verbal Review 2nd edition would do.
Coming to E-GMAT, no doubt its really good but try to learn Verbal on your own and then make a decision based on your learning.