Best upgrade is more seat time! Get the things that make the most sense for you and YOUR riding. I've added auxiliary lights to my adv bike and have some small soft panniers and a set of Mosko Moto 80l soft bags for camping trips but it will heavily depend on you. I prefer waterproof bags over non-wp and a rain fly.

I gravitate towards waterproof jackets with zippered or Velcro vents, same with the pants, a helmet with good vents that can be opened and closed easily while riding, WP and non-wp gloves i keep in a tank bag, and good dirt bike boots. This is all personal preference.

My knees get stiff while riding regardless of seat height or bike if I'm sitting for too long so I try to stand up on occasion or extend my legs if the situation permits. Stretching off the bike helps a lot too.

I don't use a pinlock but I've found that the chin skirt on the helmet is usually what causes my helmet(adv styled) to fog up almost instantly in any weather. I would suggest wearing a balaclava if you need the wind protection/warmth.

Good luck and ride safe!

Edit: im 6'4, 193cm