What are the possible ways to do a perfect inert atmosphere organic reaction without using glove box ?

You can first make sure your round bottom flask is flame dried. For this you can use schlenk adapter and butane gas.

Then immediately put a cork and Nitrogen or Argon balloon. Transfer your material in liquid form without removing the cork to maintain the inertness in the flask.

For Inert atmosphere, one can use either nitrogen or argon. First take oven dried RBF with a good quality rubber septum. Flush out the inside air with help of nitrogen balloon by using needle inlet and empty outlet needle. take needles out and add separately dissolved all starting material in solvent into RBF carefully. Again you can purge the nitrogen with balloon. or you can add first all material in RBF and then flush out air. You can also use vacuum for flushing/purging. This might be helpful to you. 

In addition to above you can use distilled DMF and distilled Et3N for your reaction. Before distilling you can treat it with NaH or LiAlH4 to almost all the water in them.

In general is much easier with Argon than with Nitrogen, because Argon is dense and sits on the bottom of the RBF displacing the air and moisture. Of course if you do not have acces to Argon, Nitrogen should work. Just do it very carefully.

I never felt the balloon transfer method was very sound. I saw a paper that measured the levels of CO2 and H2O in a N2 balloon using FT-IR and found that atmospheric conditions were reintroduced into the balloon after only a few minutes. Bull. Korean Chem. Soc. 2010, Vol. 31, No. 2 515 DOI 10.5012/bkcs.2010.31.02.515, http://ocean.kisti.re.kr/downfile/volume/chemical/JCGMCS/2010/v31n2/JCGMCS_2010_v31n2_515.pdf