I think I understand your mindset. According to me, here's what you should do based on your post:
1. I strongly recommend not targeting both CAT and GMAT. The two are different in many ways. I know this from my personal experiences.
2. Assess your chances at cracking a great percentile score in CAT.
3. If you have faith in yourself, start preparing just for CAT since you have plenty to time get a GMAT score later considering your work experience.
4. If you're unsure about your success in CAT, right now is the perfect time to begin GMAT preparation.
5. If you decide to take GMAT, I suggest you to take
e-GMAT Online course which covers both Verbal and Quants. Don't go for a coaching class. It's not indispensable. Don't worry about not having a personal mentor.
e-GMAT's lessons, questions, and especially forums will be sufficient for GMAT preparation. Plus, you can always write to
e-GMAT or on gmatclub to clarify your doubts.
I think you need to consider some first few variables before you ponder over GMAT vs CAT vs Both.
Feel free to reach out to me to discuss reasons behind my suggestions or any other advice.