>>718966043
You find a friend who has 9* in whatever stat you want. Then borrow them and use them on your runs. Until you get a 3* character in the same stat. Now you have a 6* parent. Repeat for a 9*.

The thing is though, you should focus on skill (white) stats first. Then when you have parents with tons of good ones, focus on green and blue stars. Because you want the blue stars to be the final one. But also, you can use a parent with lots of good white sparks on more umas.