A lot of variables in the magic to consider, but if you retain your knowledge, than 35 back to 15. You've essentially matured as far as you will at that point, started a family or married if you will do so, found stabilization in your career or at least moved far down that path, you hit the major milestones.

So back to 15 and then you live out the bulk of your high school with knowledge to help you actually enjoy learning, slow pace of high school, form lasting lifelong friendships, properly pursue education beyond high school, then live your 20s with a full appreciation for what they are, start saving money the right way, date the right way and invest in all of the tech companies before they get big so that you're obscenely wealthy through your late 20s and beyond.

Use the money to line a small island completely with underground dynamite charges. Invite trump, tell him you're offering him an unlimited budget to make the island into the first trump island and resort, hand him a golden shovel and say, "I'm going to get in this helicopter to get higher up to take a nice cinematic shot of you breaking ground for the press release" when you're out of the blast radius, press the button. You've done one of the greater services to humanity by any living human in history. Enjoy your earned retirement.