Tipping is a totally personal thing so is not mandatory, feel free to give what you can or think each individual deserves, if you decide you want to tip here are some guidelines to help you: Context of Democratic Republic of Congo: 900 Congolese Francs = US$1 Officially minimum wage is $3 a day/$90 a month although realistically most people live off about 500 Congolese francs per day which around US$ 0.50. $US is the main currency in use in Democratic Republic of Congo, however, the Congolese are very particular about which type of $US notes they accept, make sure your notes are printed no earlier than 2004 and are not ripped or torn Rangers.
Virunga National Park Rangers are paid a monthly salary of $130, (an average Congolese army soldier is paid $30-$40 a month) so a few dollars to each ranger would be adequate. Volcano Porters at the volcano can be hired for $12 a day ($24 for a return journey), this is their salary therefore you do not need to tip them. However, please pay them directly and do not give the money to anyone else.
Note: Most people share one porter between two people, unless they have a lot of additional equipment e.g. for a camera. Guides Virunga National Park itself does not provide guides, so it is likely your guide will be a ranger. Some of our rangers are very knowledgeable, but please bear in mind that they may not speak good English as the main languages are French and Swahili in this area.
If you are traveling with a tour operator they might provide a guide so please ask your tour operator what is appropriate for their guides. Please try to bring correct change as it is unlikely that a large note will be shared equally.