I agree with Pepsi, you can't really rely one Mejai's Soulstealer only because you dependent on kills to increase your ap power which won't do much if you don't get any kills, swapping out Mejai's Soulstealer for either Void Staff or Rod of Ages the reason why I pick Void Staff is for the extra magic penetration and Ap will be very useful over Mejai's Soulstealer and switching Soul Shroud for Rod of Ages, because it will help give health,ap, and mana which can be useful for solving your mana problem. However I suggest taking a look at the item section and exploring the Ap side of things

Good guide, aesthetics are good but 3 things you should do:
Add more chapters because this guide isn't finished.
Activate comment to vote so you won't get trollvoted.
Mejai's Soulstealer is good only if you do well and you surely have some games where you do bad...