I have completed my b.com and planning to go for MBA. I have dropped this year just for preparation.

Yes it is recommended to go with next year as there is very less rime left and would not be feasible and recommended to appear this year. Doing MCom is of no value as there is lack jn opportunities for such candidates. You can take up MBA in Finance and go for roles like Investment banking, risk management, Equity hedge fund Analysis, Private equity Analysis, Stock Decision anakyst, Wealth management, etc.

While there is nothing wrong in dropping out to prepare for cat and there are many who do the same and crack top colleges, I would suggest you to also build your profile in parallel....try out doing some virtual internships which will serve two purposes, one of which is you will get a taste about the various specialization offered in any b-school and will also add value to your profile by having some work experience. I hope this answer helps you to reach your goals.

Firstly, the choice of whether to do MCom cannot be intertwined with that of doing an MBA. Both are two different streams. One will equip you to take up roles in field of management whereas the other is more suited for core knowledge and subsequent application.

So, considering you choose to do an MBA and as you say, you've dropped an year for preparing for CAT, I would suggest that you right away start focusing on your preps. Key pointers in this regrad:
1. Given that your previous academic section lacks spikes, focus on getting a high percentile, preferably 99+.
2. Being a Bcom graduate, will help you getting shortlist for interviews and will also help you in targeting good sectors for placements.
3. Increasing diversity at BSchools (10-25% non-engineers) gives another incentive.
4. Focus not just on CAT and IIMs but also on other institutes like MDI, SPJain, XL, NMIMS.
5. It's august now. So, roughly 4 months to go for actual exam. It's a good time to start preparations in full swing. Do not waste any more time and follow a schedule.

Hope this helps!