The equivalent of US$ 15 per day per trekker is generally enough for extra expenses like shower, wifi, snacks,etc.Therefore, USD 200  converted in Local Currency i.e. Nrs. will generally be enough for the duration of your trek. It also depends on your spending habits and preferences. We also recommend you to carry as much as US$ 300 / 400 as an Emergency backup.  As for the tipping of the staff, you can always do it in foreign currency especially USD, Euros or Pounds.