Hello! I think the 50% rule means that 50% of the time you spend drawing you just draw whatever it is you want to draw. If your dream is designing jewelery - do so! If you start following along tutorials that would probably count as focused studying, where your primary concern is learning and be included in the 50% that includes the Draw a box lessons.

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To answer your question:

just sitting down and draw "something" without really knowing what Im doing?

Yes, as long as that "something" is something you want to draw!

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Hope that helps!

Do fanart, but not normal fanart

find 2 characters you like and merge them if possible put them in a scenario created based on the character

Mechanism:

This works for the same reason that novice writers merge several stories or put characters that are not their own in alien situations for them, it helps your creativity and removes blocks.

Another option would be to brainstorm ideas, objects etc and draw based on this.

If you have artistic block, I recommend you meditate or go for a walk

In my opinion I think you should do what you want. Reading Lesson 0 in regards to the 50% basically says to draw things you want, even when you lack the skill.

Watching and following tutorials is a good idea (I have been looking at some portrait tutorials), but I would not stress too much. I don't know much about jewllery, but I found some tutorials on YouTube:

https://m.youtube.com/watch?v=Szw9ki8UAZ4

https://m.youtube.com/watch?v=67A8uRFU920 (she starts at the 1:15 mark)