Which was the most important long-term effect of Rome's frequent civil wars in the 200s CE?

They damaged the economy

Explanation:

As the civil wars occurred, the majority of the empire's resources were kinda wasted through the war. For example, large portion of the agricultural production was used to feed the soldiers and large portion of their metal was used to make weapons.

This left very little goods that they can sell to the people outside their empire. On top of that the expense that occurred from the damages to their cities also extremely expensive. All of these factors contribute to the damage on their economy.