yea clarity is a just in case you run out of mana because if your versing someone that is a pro you may need it for things like if they try to under tower you (its happened to me it was awesome i won in the end of that under tower). you can get what ever spell you wont instead of clarity or you can get fortify. i don't have wisdom runes as well i just like them (you don't have to you can get something like mana regen).

maybe that pro heirmerdinger was me lol

Oh yeah I forgot to mention I don't have wisdom rune so I use something else which is okay.

Very nice. I saw this pro Heimerdinger soloing top and I can't find any guides on how to do it until I saw yours. But I never need to use clarity. I suggest changing clarity for something else. Like ghost or something.