My client has bought license with production and fir the first 3 months he wants us to setup trade and inventory and finance modules so my doubt is can i setup only those two modules now and production module later if so wat r the precautions i have to take for doing so
Well yes you can do it but depending upon the business the considerations differ.
No accounts transactions from production can take place, and no material consumption or output would appear without item journals where the posting is different. There is no production paperwork or tracking, any items supplied by production order through planning will not, it also depends if you put the BOM in.
You need to analyse the system and business for the implementation. It is not my preference, but if properly planned and managed there are no real issues.