I'm poor...
I'm not talking about using Dropbox to transfer everything but about using Dropbox to read comics on the fly, reading 'online' if you will. Or you can put a week worth of comics available in offline mode and that will be what, 5gb at most?
A Pro is fucking expensive and really a major investment that's not worth it. I played around with one - it's good if you want to play graphic intensive games but that's a bit stupid if you have a PC or console.
I pretend not be a geek but this is being written on a iPhone 7 with 128 gb... I'm thinking about getting a 'new' iPad but I'll buy a used previous gen when the next comes out.
I must protest. Pros are incredible and definitely worth the investment based on screen space. I have extensive experience with the Pro owned by my friend. The 13" screen is a big deal, if that's what he wants, and what separates it among tablets. Furthermore, I've never heard anyone complain about spending too much money on the bigger storage models of iPads. Ever. Not once. This goes back half a decade. I've heard dozens of friends bemoan that they didn't opt to spend more for a bigger model who got the baseline.
Alternatively, he could try finding an old
iPad Air 16GB new for ~$300.
He would be relatively miserable with it: watching uploads crawl, not being able to access his material when he's on the road and out of cellular range, dealing with the hassle of a fragmented library across devices and maybe forgetting where he has what, etc. Then there's always the fact that the iPad Air has some serious weaknesses against it as a piece of hardware:
http://www.gsmarena.com/compare.php3?idPhone1=5797&idPhone2=7562
A
much weaker processor, 1/4 the RAM (this is going to matter dealing with libraries his size), inferior display size (one of the biggest costs of producing a tablet), inferior resolution, inferior LTE speeds for the Cellular versions, inferior WiFi standard, inferior cameras, no NFC, no fingerprint sensor or barometer, and maybe the biggest drawback: USB2 vs. USB3. Supposing he has a PC/laptop with USB3 this will make a massive difference in transfer speeds for large chunks of files. It makes just as big a difference in charge times. It also lacks a Stylus and pressure sensitivity. Fun for drawing.
Dropbox is cool. Calibre networks with Dropbox. It can automatically output portions of your library to Dropbox. Hell, you can choose to store your library in the local folders where your Dropbox is pointed to sync. In fact, there's even a Calibre app on Android called "Calibre Cloud" that allows you to access it, and integrates with any of the Cloud services if you happen to prefer a different one:
https://play.google.com/store/apps/details?id=com.intrepidlogic.calibrecloud&hl=en
Bottom line is that Calibre makes it unbelievably easy to move all of your content around: to any app or platform or service. So use it to move stuff to Dropbox, then use a comic viewer like Perfect Viewer to access and browse.
The above are all rudimentary solutions. If you really know what you're doing you just open a port with password protection and run an OPDS server that stays on at home all the time. On the go, you can access and browse your entire Calibre contents, as a lovely bookshelf (such as it would appear in iBooks or Aldiko), no matter how large your library, from out in the world, via cellular networks or public WiFi or whatever, without paying superfluous subscription fees for larger storage space with the Cloud services like Dropbox. Those services are designed to milk you.
With one click you can download any book in your library, directly from where you browsed to access it in your app (I use Moonreader), remotely, straight from your PC at home. Great strategy if you know you're about to head into wasteland of cellular reception. Just click the "Import" button and it downloads the selected book(s) you're currently reading to the local storage, and you're good. Now you don't need internet to continue reading.