Celerity feels weak for ad champs

So, I enjoy fleet footwork on fiora, and decided to change my runes from healing based to movement speed based, taking celerity I went to practice tool, took ghost. with ghost active, swiftness boots, trinity phage proc, fleet proc i only managed to get a mere 10 ad, had I put in a bot and hit a vital while ulting, maybe up to 12-14 ad at most, I understand it's in the sorcery page, i'd just like to see it have some use on ad champs.