What kind of toner should I use to get my hair a white/platinum blonde ?

I've just bleached it to a very light blonde and would like to keep it this way without it ever becoming yellow. I have never used a toner before and I am looking to purchase it at a Walgreens or Target maybe.. ? And it won't be damaging to my hair .. right ? I have heard that toners are conditioning.What kind of toner should I use to get my hair a white/platinum blonde ?
you could just add a little lemon juice to your shampoo. I heard that helps

Fish