Flutter Correct Use of Interstitial Ad

In an article I read before, when showing interstitial ad, it was stated that the ad must be shown first and then the transition must be made.

I set ad impressions by number of clicks. Is the code I wrote correct or is there a main usage condition.

I tried two methods and I'm not sure if they are the right methods or not.

Ad controller

class AdController extends GetxController {
  InterstitialAd? interstitialAd;
  int adCounter = 0;

  void onAdLoaded(InterstitialAd ad) {
    interstitialAd = ad;

    interstitialAd?.fullScreenContentCallback = FullScreenContentCallback(
      onAdDismissedFullScreenContent: (ad) {
        interstitialAd?.dispose();
        initAd();
      },
      onAdFailedToShowFullScreenContent: (ad, error) {
        interstitialAd?.dispose();
        initAd();
      },
    );
  }

  void initAd() {
    InterstitialAd.load(
      adUnitId: AdHelper.interstitialAdUnitId,
      request: const AdRequest(),
      adLoadCallback: InterstitialAdLoadCallback(
        onAdLoaded: onAdLoaded,
        onAdFailedToLoad: (error) {},
      ),
    );
  }

  void getAd() {
    if (adCounter % 15 == 0) {
      interstitialAd?.show();
    }
    adCounter++;
  }

  @override
  void onInit() {
    initAd();
    super.onInit();
  }
}

First Way

 GestureDetector(
      onTap: () {
       gDealsAdController.getAd();
        
       Get.to(
        const GameDealsIndex(),
        transition: Transition.native,
        duration: const Duration(milliseconds: 200),
        arguments: gDeals,);})

Second Way

child: GestureDetector(
                      onTap: () async {
                        //todo:
                        //gDealsAdController.getAd();
                        //todo: ads try

                        if (gDealsAdController.adCounter % 10 == 0) {
                          await gDealsAdController.interstitialAd?.show();
                        }
                        gDealsAdController.adCounter++;

                        Get.to(
                          const GameDealsIndex(),
                          transition: Transition.native,
                          duration: const Duration(milliseconds: 200),
                          arguments: gDeals,
                        );