"Where do I start with to improve my interests?"
Since you are asking this question in this topic, which is about Original Nobility, why not try to recover your earlier tastes?
"who I am since I was a teenager"
Can you recall a time prior to your teenage years when you would have disliked the music you ended up liking as a teenager? If so, then you might be able to recover that earlier condition. On the other hand, if you tell me that you would have liked the same music even at a younger age, then there is no hope for an Original Nobility pathway for you.
"What do you think I can improve on as a leftist, and what potential do you think I have as a leftist?"
It would be easier for me to judge if you:
https://trueleft.createaforum.com/volunteer/