What would the advantages be of someone who can photosynthesize? If that were someone's power, how could they maximize it's use? (It's plausible that they would also have minor abilities that stem from their ability to photosynthesize).
Assuming that the question isn't answered by some of the existing human photosynthesis questions elsewhere in Worldbuilding, the skinny on the concept:
Humans aren't particularly well-adapted to photosynthesis (since we don't do it). We don't have much surface area in proportion to our energy use, which is why we consume other things that do photosynthesis at one, two, or even three removes (either they do it themselves, or they eat things that do it, or they eat things that eat things that do it).
Even assuming that your character goes nude, all they'd have is a slightly reduced appetite; they'd still need to get most of their calories from ingestion. Additionally, even assuming they were also altered to somehow got by on the very limited sugar synthesis sun-exposed photosynthetic human skin could manage, they'd still need to eat to gain essential nutrients that humans need.
So, tl;dr: A human with photosynthetic skin would not have any substantial advantage over one without.
(In answer to the second question, to maximize its use, they'd probably want to go nude, but there are only a limited few places on earth where humans can reliably and comfortably do that. So to maximize its use, they might also want to move somewhere consistently sunny and at a temperature where they could go nude, and with a social climate that allows them to do so.)