Always take cash with you. For example, on Easter Island in San Pedro ATMs run very soon out of cash and in Futaleufú National Reserve there is only one ATM.
Flying from Russia and Ukraine and making connection to another flight in Madrid is cheaper than a direct flight to Chile. You can also fly to Buenos Aires and from there go to Chile by bus.
For 20 thousand peso you can explore all the main attractions of Santiago on hop-on ho-off buses.
Tickets can be bought here turistik.cl/tour/santiago-hop-on-hop-off