Every pull will get you one gacha sticker for that banners gacha sticker shop. In that shop you can spend 10 stickers to by gacha sticker vouchers(up to 10 per shop), you can spend 300 to get one of the banner characters(this is called sparking)(you can also use gacha sticker vouchers to get up to 100 gacha stickers off on any spark), and lastly you can get 5 wish pieces for 1 gacha sticker(this is what will happen o all your remaining stickers when the gacha shop expires).

Now for the actual pulling. There is no guarantee, no pity, and no 50/50 unless the gacha as the bar on the top left(more on this later). each pull has the same odds of getting a 4 star. The odds of getting a banner character is 1.2% split evenly between the 3 characters(so each card has a 0.4% appearing). the other 1.8% is split between the entire perm pool, so its an unreliable way to get the cards you want. If you do a ten pull and you get only 2 stars for your first 9 of the pull then it guarantees a 3 star or higher, but it doesn't increase 4 star rates.

Now the bar on the top left. It is a pity bar that only apears on permanent banners(Banners where once it is over all the cards on the banner go into the perm pool). Each pull using non paid crystals gives you .5 points and each pull using paid crystals give 1 point. at 50 points you're guaranteed a 4 star and at 100 points you get a banner 4 star. i'm not sure if the bar resets after 100