If you stole the
Chronovisor from the Vatican and used it to build a time machine, what would you do with it? Assume the machine could go forwards or backward in time with equal facility, and that it was self-powered so you couldn't strand yourself somewhen with no way to return - you are a free agent in time, no longer bound by causality, physics, or the need to wear binding, confining pants!
For me, I'd go back 20 years and give my younger self portable wealth (like gold coins or Michael Jackson commemorative dinner plates) and a printout of the best-performing stocks of 1989-2009. Then I'd give him a list of all the friends I've had that have made terrible life decisions - like suicide, addiction and getting married to high society hosebags - and tell that "earlier me" to do whatever he can to stop the madness.