Been to Moscow a few times, a nice city lots to see. Not been for a couple of years for the obvious reasons and never there for more than 4/5 days. £, $ or € are accepted in some places and so are cards just about everywhere. So never changed a large amount of cash. Usually £100 is more than enough with everything else going on cards. Yandex go for taxis (Russian Uber). $ to Rubble used to better than £ not sure if it still the case. Have changed cash at both Russian and uk Airports and Russian bank. Uk airport was the worst rate, but only did it once