afaict it uses engagement to determine what you like, so

- watching the video completely

- liking

- commenting

- sharing

increase your account's affinity to the tags associated with that video. If you like multiple videos with the same tag, you'll start seeing many videos with that tag. So, I think searching for a few tags about topics you're interested in and liking a few videos will prime the algorithm enough to make suggestions start being relevant.

This can also be annoying - I must have liked a few vids about dnd, and now i get more dnd suggestions than I want.