Hi Rajasekhar,
As Dave mentioned above , please detail the features that you want to use from SAP GTS for your scenario.
Basically, Third Party Scenario is a mix of SAP Sales and Distribution & SAP MM areas, hence there will be no more unusual requirements for SAP GTS customization. The process for both the areas will go hand in hand. If getting stuck at some point, please let me know for more details.
Regards,
Aman