Mr. Lex, It is to be noted that ancient India were composed of many tribes. Buddha was  approximately born in 563 BCE according to scholars and historians. So at this time, there were many tribes and small kingdoms. Early Vedic texts attest several Janas( tribes) living in semi-nomadic tribal state, fighting among themselves for cows, sheep and green pastures. This was literally a period of Maha Janapadas(700–300 BCE).
The term "Janapada" literally means the foothold of a tribe.

During the Mauryan Empire period which existed approximately from 321–184 BC, many of the tribes were rounded up during  the expansion to bring them under Mauryan control. King Ashoka of the Maurya Dynasty ruled almost all of the Indian subcontinent from 269 BC to 232 BC. One of India's greatest emperors, Ashoka reigned over most of present-day India after a number of military conquests. His empire stretched from present-day Pakistan, Afghanistan in the west, to the present-day Bangladesh and the Indian state of Assam in the east, and as far south as northern Kerala and Andhra. But the Himalayas region including Lumbini were beyond the reach of Asoka. At this stage, King Suddhodana Gautama of the Shakya tribe was ruling the Kapilavastu region near Lumbini while the Kathmandu valley was the Kirat kingdom. Kiratdesa referring to Nepal and the surrounding Himalayas region is listed as as one of the many ancient kingdoms in the vedic and other puranic works.

Hope this help.