quick state machine

const int MaxState = 8;
int state = 1;
unsigned long currentMillis;
unsigned long previousMillis;
unsigned long interval=2000;
//arrays are zero based, so ignore the first element
//fill this with the pin numbers of your LEDs, in order
int ledArray[] = {0,1,2,3,4,5,6,7};
void loop() {

  currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    digitalWrite(ledArray[state], HIGH);
    state++;

    if (state == MaxState) {
      // turn off all the LEDs
      state = 1;
    }
    previousMillis = currentMillis;
  }

}