Well, although higher IVs are better, it doesn't have to be an absolute show-stopping factor if you plan to use it in competitive play, you just have to invest your EVs more mindfully. When I say the nine shiny spreads, I mean the nine shiny-possible natures and the set IVs they're programmed to have. You can trade for the other natures but the GTS blocks all shiny Jirachis, however there is a way to upload ribboned/shiny Jirachi to PokeCheck but the way to do it requires the use of a program that is forbidden to speak of here and how they get past the GTS that with the forbidden program is unknown to me.