unsigned long prevMillis = 0;
unsigned long prevMillis2 = 0;
unsigned long prevMillis3 = 0;
unsigned long prevMillis4 = 0;
unsigned long prevMillis5 = 0;

// Counter (seconds)
int counter;
int counter2;
int counter3;
int counter4;
int counter5;

// Finite state machine
#define COUNTING 0
#define DISPLAY 1
int State;

#define COUNTING2 0
#define DISPLAY2 1
int State2;

#define COUNTING3 0
#define DISPLAY3 1
int State3;

#define COUNTING4 0
#define DISPLAY4 1
int State4;

#define COUNTING5 0
#define DISPLAY5 1
int State5;

const int ledPin =  LED_BUILTIN;
int ledState = LOW;
unsigned long previousMillis = 0;  

void setup() {
  Serial.begin(9600);
  
  pinMode(ledPin, OUTPUT);
  
  // Starting values
  counter = 5; // milisecond convert
  State = COUNTING;

  counter2 = 2; // milisecond convert
  State2 = COUNTING2;

  counter3 = 5; // milisecond convert
  State3 = COUNTING3;
  
  counter4 = 2; // milisecond convert
  State4 = COUNTING4;

  counter5 = 5; // milisecond convert
  State5 = COUNTING5;

  prevMillis = millis();
  prevMillis2 = millis();
  prevMillis3 = millis();
  prevMillis4 = millis();
  prevMillis5 = millis();
}

void loop () {
  test();
  
  if (millis() - previousMillis >= 1000) {
    // save the last time you blinked the LED
    previousMillis = millis();

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);
  }
}

void test() {
  switch(State) {
    case COUNTING:
      // the device you want to turn on first
      if(millis() - prevMillis >= 1000) {
        prevMillis = millis();
          Serial.println(--counter);
        if(counter <= 0) {
          State = DISPLAY;
        }
      }
      break;
    case DISPLAY:
      switch(State2) {
        case COUNTING2:
          // the next device after the first is done
          if(millis() - prevMillis2 >= 1000) {
            prevMillis2 = millis();
              Serial.println(--counter2);

            if(counter2 <= 0) {
              State2 = DISPLAY2;
            }
          }
          break;
        case DISPLAY2:
          switch(State3) {
            case COUNTING3:
              // the next device after the first is done
              if(millis() - prevMillis3 >= 1000) {
                prevMillis3 = millis();
                  Serial.println(--counter3);

                if(counter3 <= 0) {
                  State3 = DISPLAY3;
                }
              }
              break;
            case DISPLAY3:
              switch(State4) {
                case COUNTING4:
                  // the next device after the first is done
                  if(millis() - prevMillis4 >= 1000) {
                    prevMillis4 = millis();
                      Serial.println(--counter4);

                    if(counter4 <= 0) {
                      State4 = DISPLAY4;
                    }
                  }
                  break;
                case DISPLAY4:
                  switch(State5) {
                    case COUNTING5:
                      // the next device after the first is done
                      if(millis() - prevMillis5 >= 1000) {
                        prevMillis5 = millis();
                          Serial.println(--counter5);

                        if(counter5 <= 0) {
                          State5 = DISPLAY5;
                        }
                      }
                      break;
                    case DISPLAY5:
                        prevMillis = millis();
                        State = COUNTING;
                      break;
                  }
                  break;
              }
              break;
          }
          break;
      }
      break;
  }
}