Well, if you want to get a shiny in the beginning, all you can do is reset until you get one. However, if you just want a shiny, you can either trade a ditto from FR/LG/E or reset until you get a female (which wouldn’t take as long as resetting for a shiny) and breed until you get one. This would still take a long time. Unfortunately, I don’t believe RNG abuse (a method to obtain shinies) works unless you have D/P/P/or Emerald. You could increase your chances of hatching one by using the Masuda method (breeding with an international pokemon), but since you don’t have wi-fi with sapphire, obtaining a national pokemon is obviously very hard. Good luck!