This is outside your price range but hear me out, I’m talking about this because you’re referring to a backup drive. I’ve had some very sad losses in the past and have no intentions of losing my media again.
I purchased a Drobo and am quite happy with it. Its significantly more expensive than what you’re looking for but it has been worth every penny. It uses a backup redundancy setup something like RAID5 where the data is duplicated across the drives you place in it (up to four). A lot of people simply offload their media onto an external drive and consider it safe but as soon as that drive fails you’re screwed.
Incrementally copying your files is a bit better but you are then assuming that you will be prudent it keeping your files updated (I know I can’t do that). With a redundant external storage system you simply use it as a main storage container and let it handle the backups. Considering that SATA drives are stupid cheap these days the unit practically pays for itself in my opinion.