What toner can I use before applying The Ordinary Niacinamide?

Any toner will work. Niacinamide is compatible with almost all ingredients

you can pair your niacinamide with Hyaluronic acid toner or any basic hydrating toner. I believe you can use the glycolic acid toner that you currently have, it really just depends on how your skin can handle both ingredients, they won’t clash with each other, but the niacinamide is 10% which is quite high, perhaps you can try first to see if your skin can handle it. I personally am using a 5% niacinamide serum and I basically pair it with any toners on hands, for your reference I will tag my toners here. ☺️

This is a great hydrating toner, without exfoliation

I will recommend you this one, this toner so mild, so it's perfectly fit for sensitive skin and maybe for newbie too^^

You can use it with hydrating toner, that have ingredients like hyaluronic or centella asiatica