Depends on your budget and your needs:
If you need access only when at home, you can go with a USB external drive. There are tons of manufacturers with tons of sizes, pick based on reviews,
features and pricing at that point
If you need access on the go when you do not have internet access, get a large USB portable (WD makes a 3TB - I use that for media while traveling)
If you need access on the go when you do have internet access, get a external drive with cloud accessibility (WD & Seagate both have good consumer platforms, I went with the WD MyCloud because of the storage expansion capability).
My setup is tiered - I use a large capacity storage drive in my workstation, I backup to a USB non-portable drive once a week, I use a large capacity portable drive with all my media files on it for travel and I use a USB external with external network access so I can share files across multiple workstations. It's not cheap, but it's effective.
If I were in your shoes, I would get a high-capacity portable drive. Bring it with you wherever you go so that it doesn't matter if you're on a flight, you can still work with ease