Instead of languishing there he left Bosnia and Hercegovina in 1872 for Belgrade, where Archimandrite Nićifor Dučić, a family friend, found him a job as an apprentice in then famous store held by Radosavljević & Ignjatijević.

After the war, with the support of his countrymen, Trieste traders Aleksa Krsmanović and Rista Parnanos, Ćelović started his own business as an independent merchant, selling plums, corn, wheat, and pigs.

Ćelović also did a lot to help the weaker member of society, founding the Committee for the Protection of the Blind Girls in Belgrade.

It stemmed from the period of his life, during which he was part of the Chetnik movement, when he became closely connected with Milorad Gođevac, general Jovan Atanacković and the students from Old Serbia (now Macedonia), leading him to the lifelong conviction that education was the basis of the Serbian future.

Printing of the Glasnik Hemijskog Drustva Beograd (Bulletin of the Chemical Society) with Nikola A. Pušin as editor and chief, was enabled thanks to financial assistance from the Luka Ćelović-Trebinje Fund.

Apart from being a successful businessman, Ćelović was also supportive of common welfare, he and Dr. Milorad Gođevac, a Belgrade physician, were funding troops to fight for Old Serbia.

The first president was Luka Ćelović and the other leaders of the campaign were Vasa Jovanović, Ljubomir Kovačević, Žika Rafajlović and Nikola Spasić.

The men solicited for the cause, and Luka Ćelović donated the enormous sum of 50,000 dinars annually to the Četnik Campaign.