What size external hard drive should I get?

I ran out of space on my Mac so I'm looking for an external hard drive. I mainly use my laptop for school work and making vids/storing pics. The videos take up the most space.

My laptop has 121 GB and I used up 120.12 GB.
69.6 GB is for movies.

I make videos with a GoPro so I think that takes up a lot of space. What would be a good amount of storage for an external hard drive? Is 1 TB fine?

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