realistic: Go back to the last lotto drawing and pick the numers that won.....
Ideally: Travel back to every time instance that has caused a conspiracy.....and find out the truths.
Did we really land on the moon
The real history of the Knights Templars, Illuminate, Masons, and the inside workings of the catholic church. (nothing against ANY of these, especially the church, but it is it's own government so there has to be a conspiracy somewhere...you would think
Who fired the first shot in the "Civil War" in the US
I'd go back to when I was very young and get my younger self focused on better role models than my parents, so I would learn what self confidence and self esteem really are at an early age. It's much harder to obtain those things as an adult when you've had bad role models your entire life.