No matter which iPhone you buy, you’re getting Apple’s first-class ecosystem, security and updates, as well as the App Store, which has the best selection of apps. Since all of these iPhones run iOS 11, they all perform and behave very similarly. You'd be hard-pressed to notice the differences between the iPhone 7 and iPhone 8, in particular.
If you're still having trouble seeing the differences between the iPhone 7, iPhone 8, and iPhone 8, I highly recommend checking out Apple's iPhone comparison tool. But if you need further convincing, consider this: The iPhone 8 is a basically slightly faster iPhone 7 with a glass back for wireless charging. Would you spend $150 for those changes, especially knowing the phone doesn't come with an included wireless charging pad? Try everything in store and see for yourself, but I'm not convinced wireless charging is worth investing in quite yet. Wait until charging systems are better, cheaper, and more ubiquitous — it'll be a much better market by this time next year, for instance.
And if you're really holding out for the iPhone X, my question is this: Why? Sure, some of the features on that phone are exciting, but are they worth paying nearly double the price of an iPhone 7? That is a question you'll need to answer for yourself.
Consider this as well: By this time next year, we're going to be talking about an all-new iPhone, which means the iPhone X will be less expensive by then, and definitely more available than it will be if you're trying to get a new iPhone before the end of the year. Simply put, there's no real reason to obsess over the latest phone when there's nothing really wrong with the iPhone 7, last year's "all-new" phone. It has an excellent design, a gorgeous screen, and great battery life. And at $549 to start, it's a steal.