The Garnier Olia hair dye I use is the color 1.0 Black (zwart nacht = black night in English). One package actually is enough for my hair (cut in layers). And there retail between 10-15€ a package, which is a bit more expensive for at home dye.
Since I only dye my hair every three months more or less, I use 4 packages a year, so I can look out for promotions and just stock on the dye I need. If you have to dye your hair more often (for ex. if your hair is much lighter) you will need more dye (logic).
I give this dye a 8.59/10 since it is super good dye, smells good, and the conditioner you get with it is amazing. The only downside to me is packaging, it is a lot more wasteful than it could be, and I think that's a shame.
I can highly recommend getting this dye as it will make your hair super soft and the colors are vibrant with a healthy shine to them.