I think there are two ways to do cloud storage:
Be a huge business, so large that you can run your own data centres or negotiate very cheap deals with the cloud giants.
Be a tiny business, so small that you can operate within the free allowances of (possibly multiple) cloud providers.
Everything in between is difficult.
More generally, realistically you can't compete with Instagram. You need to offer something sufficiently different that it is not competing, and then charge your users enough to cover your costs.
Or, there is this popular approach: find an investor with lots of money and run the business at a loss (while paying yourself a good salary). When the investor doesn't want to pay any more, close down the business and walk away. Even if this business model doesn't appeal to you, it's important to be aware of it because it may be what your competitors are doing.
Good luck!