Dear Mr.Varma Alluri,
I appreciate your interest on SAP ERP.
Based on your interest you can choose any module ( technical / functional ).Each module has its own importance in real time.
If you want learn more about any / preferred module, you can always access help.sap.com which will give you a list of results and among them you can choose whichever link you want to start studying on that subject.
Based on your research choose a right module which suits you better.
Based on your experience I believe that the below functional modules will be more suitable for people who has some Business / Domain / experience . Just think & try to follow the SAP Help to take a right decision.
MM – MATERIAL MANAGEMENT ( More about Purchasing related activities / Goods receipts / Inventory Management / vendor management )
PS–Project Systems ( more about your projects / activities / wbs..Etc)
Below link may helps you.
http://scn.sap.com/message/15119811#15119811
Wish you all the best.
Regards,
N.S.Rao