You can get the needed stones on Aqua Shadows maps, in the Blue Medal shop or craft them from lower rarity stones (but it takes an eternity) or from rainbow stons for golds one. Then, you need 8 gold stones for 5* girls equipements and 10 rainbow stones for 6* girls equipements. Unless you have tons of money and forge spirits, I think evolving personnal equipement is not something new player should bother with. It takes a long long time, a lot of stamina and don't give good enough bonus to be a priority. It's good when you have already really solid girls to me them better but it will not change your life at low level. Just focus on classic event equipement. It give so much more stats then personnal equipements.