If your website already looks good on a phone, why bother with an app? if your site is such that you get a fair amount of visitors or frequent users, you can create an additional income stream from either charging for your app or by displaying hopefully unobtrusive ads.
Unfortunately, I mostly found the dedicated "app builder" services to be more expensive than even the better website builders that provided much more functionality to their customers, particularly since most of the work was already done by the website builders in creating a responsive site. I did find one easy-to-use free site at appsgeyser.com and converted my website as a test case in less than ten minutes. You can find the links to download my Android app on my homepage or by scanning the QR code or by clicking here. Unfortunately, I've read that the Apple Store will not accept just a simple clone of your website.