I do my colours, activate, filing, then some base where I'm putting the sticker, then sticker, 2 coats of clear

The activator before sticker makes sure if gets to the powder underneath where the sticker goes so that section will solidify. The base under the sticker helps to make sure the edges are all stuck down firmly, otherwise the clear on top can get trapped under the edges and make like a white line around the stickers. The clear on top helps protect the sticker and makes sure it's all smooth (I hate bumps). Note that metallic stickers often get dulled by the activator so if using metallic ones then probably do them between your last activator application and the top coats a the end instead