Minimum recommended balance for all default settings should be 200 times of margin required to open minimum allowed lots size by broker at 1:100 leverage. Say you broker needs $10 to open 0.01 lots size @ 100:1 leverage, then there should be minimum 200x10=$=$2000 in account balance. Recommended amount also display on top left corner of chart in MT4. So this recommended amount varies as per your account type and leverage.
  • NB: above margin requirement is just for safety purpose and this is not hard-n-fast requirement. (If you have sufficient amount then you can run 2 pairs with default EA settings).