cassiopiea question

There's nothing wrong with that build although I'd replace Luden's with a Abyssal or a Zhonya's depending on who can blow you up (and the 40% CDR). That being said - your full build cost 18,900 gold. Very rarely will you get to that point and if you're blowing up faster than you can do your consistent damage than it's better to ditch of the offensive items for a defensive one.