First you have the nomads, who just loot an area and then move on to the next.  These are the largest and dominate the news.  These include the official government and major opposition groups.  Most offensive actions are actually raids into the territory of a rival, and peter out as soon as the troops have more loot than they can comfortably carry.

 

Then there are the resource based gangs that control specific geographic locations with valuable resources that can be sold, like diamonds and tantalum.  These gangs also handle most of the smuggling.  These gangs are generally the smallest, but have the highest per capita income, and are the best equipped and lead.  They prefer to avoid fighting and are seldom in the news (it's bad for business).

 

Lastly, there are the refugee based gangs/guerrillas.  These gangs are based in camps set up by international donors for conflict refugee from neighboring nations.  These gangs keep the local population under tight control so that they cannot leave and so the flow of donations that can be looted continues.  These gangs are mostly in the news because  of they attack the ruling factions in their old country, which then threaten to follow them back into Congo to destroy their bases if the Congo government does not.  The Congo government is not interested in doing this because of the cost and lack of potential loot, but cannot allow the foreign governments to invade because they would probably just keep what they can occupy.