What kind of UK VISA to apply for? (London)

Hello! I'm an American wishing to relocate to London. I lived in London Protected content , working as an expat, any my visa at the time was sponsored. This time, I'm going to have to apply on my own.

I'm a marketer and would like to explore both interim and permanent marketing roles ... starting with interim Protected content engagements). Can anyone advise on what type of VISA I should apply for, and any tips in applying to ensure success?

Thanks!

Lori