The gym is a fantastic tool to help get you to your goal physique but I can promise you that a gym membership alone isn't going to see you very far into your transformation.
Firstly, you need some TRAINING KNOWLEDGE on what you actually need to implement into your daily regime to make your body change. You need to learn how to train in a way that's specific to your goals and know how and when to progress your training. Whether you outsource this to a Personal Trainer or read up and learn enough yourself, you can't just rely on turning up to the gym and hoping the rest looks after itself.
The next big key is NUTRITION. This really is where most people come unstuck, especially where fatloss is concerned. Your gym might have the most expensive state of the art equipment going and you could be in there 7 days a week slogging your guts out but if your calorie balance is out of whack (you're taking in more than you're burning) your body fat is going nowhere. Understanding nutrition and your specific nutritional needs doesn't need to be overly complicated. You don't need to understand everything, you just need to understand enough.
Lastly and probably most crucially is your MINDSET. Being dedicated enough to turn up to the gym is awesome, but where that dedication comes from is what's important. If it's simply a messy Ibiza weekend in a few weeks, chances are your physique isn't going to budge much, and definitely not long term. Everyone has their own motives and I'm not here to tell you what is right or wrong in that sense, but what I will say is those who have a deep rooted, internal motivators in my experience are the ones who bring about the greatest physical changes that only improve more and more as time goes on. Maybe you want to be more confident in social situations, perhaps you want to be the best role model you can for the sake of your kids or maybe your lack of physical health is harming your business?
There are so many more important aspects than just the three I have highlighted, but I guarantee if you get your head around just those you will drastically improve your chances of finally gaining the physique you want.