Sunitha,
Welcome to the World of SAP BI!
Please pick one area to start (i.e: SAP BW or SAP HANA) and learn the area and since you are new, also plan on getting certified. If you opt to do functional area - you do not need to lear SAP BI (BW or HANA) - stick to one area that you think you can bring value.
Based on your data integrator knowledge and background, I suggest BW or HANA as a better fit.
Good luck!
Rama