The local currency in Rwanda is the Rwandan franc and money can easily be changed in Kigali before you head off into the mountains.
The economy is quite cash based, though some big hotel chains may accept credit cards or debit cards. If you are exchanging from US dollar, you must ensure that the date on the notes is 2006 or newer. Older bills won’t be accepted. The higher the value of the note, the better the rate you will receive. For example, you will get a much better rate for exchanging $100 notes compared to $20’s.
In restaurants you are not expected to tip, however it is nice to show your appreciation with a tip if the service was good. For guides, rangers and porters in National Parks we recommend between $5 and $20 per day, for drivers we recommend $15 to $25 per day.