hi Neha ,
SAP HR/HCM is definitely a great career option but you have to keep in mind that it is changing very fast .
Also depends on what you are looking to do in the SAP HCM Domain , they are whole lot of options available for e.g you could be Functional Consultant , Technical consultant(ABAP) , Admin and others .
You also have to realize that SAP HCM has changed a lot , now with Successfactors they are offering cloud solutions for all Talent management processes like Performance management , Goals management , Compensation , Recruiting , Succession management etc.
Since SAP has already made it very clear that Cloud is the way forward , so I believe that focusing on Sucessfactors may be a better deal(here i am not saying SAP on premise is not moving forward) .
Also many of the SAP HCM Consultants have already jumped on this bandwagon and are working on various Successfactors projects .
My advice would be that if you are looking to permanently work on SAP HCM/Successfactors only some online training would not help .
Certification will definitely help you in the long run , also nowadays the clients are looking at Certified Professionals , you can get a lot of information on the SAP / Successfactors sites (Certification details , course materials , Costs etc.).
Also do remember that the CORE HR Process knowledge is very much essential in the SAP HCM Consulting business as you would not be able to contribute /perform to the client if you are not able to understand the various business processes of the client .
Lastly getting on the SAP HCM/Successfactors field requires lot of hardwork ,commitment ,ability to learn and update new technologies , so once you are into it then there's no looking back.
Let me know if you have any more questions .