I'm sorry, I don't quite understand your question. Cratejoy is a monthly subscription service. Do you mean you are offering a monthly subscription on Cratejoy and want to turn it into an app?
Yes, I would like to turn my monthly subscription service into an app.
Okay, we'll if you are wondering "could I do this" then the answer is "yes". If you are wondering "if I should do this" then the answer is "probably no". If everything is hosted on Cratejoy then you app will merely be a wrapper around your website. Apple will probably reject this from their App Store as it is something that they look for in their guidelines. As well I'm not 100% but Apple/Google may want to force you to use their billing service so they can take 30% of the money you make from each subscription you sell. This will be on top of whatever cut Cratejoy takes.
Without knowing much more than the two lines of detail that you've provided I'd suggest that your best way forward is to make your Cratejoy website as mobile friendly as possible. This way you will work on all platforms without having to invest money/time into building an app and Apple/Google won't try and take a cut of your subscription.