Dacia was bounded in the south approximately by the Danubius river (Danube), in Greek sources the Istros, or at its greatest extent, by the Haemus Mons (the Balkan Mountains). Moesia (Dobrogea), a region south of the Danube, was a core area where the Getae lived and interacted with the Ancient Greeks. In the east it was bounded by the Pontus Euxinus (Black Sea) and the river Danastris (Dniester), in Greek sources the Tyras. But several Dacian settlements are recorded between the rivers Dniester and Hypanis (Bug River), and the Tisia (Tisza) to the west.
Burebista statue in the Municipal Park of Călăraşi
Burebista (Ancient Greek: Βυρεβίστας, Βοιρεβίστας) was a king of the Getae and Dacians, who unified for the first time their tribes and ruled them between 82 BC and 44 BC. He led plunder and conquest raids across Central and Southeastern Europe, subjugating most of the neighbouring tribes. After his assassination in an inside plot, the empire was divided into several smaller states.
The development of a La Tène-based economy in 3rd-2nd century BC allowed the consolidation of political power through tribal unions. Such regional unions were found both among the Transilvanian Dacians (under the rule of Rubobostes) and the Moldavian and Wallachian Getae (with a center of power in Argedava). Burebista was the first to create a union of tribes of both Dacians and the Getae.
This tribe alliance was probably a weakly centralized state, with a military organization, similar to the one of the Hellenistic Kingdoms. The exact degree of centralization is still under debate, with some archaeologists, such as K. Lockyear, denying the existence of a state, because the archaeological evidence shows much regional diversity, with only a few regional-wide trends. Other archaeologists, such as A. Diaconescu, dispute this and consider that there was a centralized political structure. Nevertheless, due to a number of archaeological factors, it's unlikely there'd be found a definite answer to this question.