Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This is my first League of legends build, and I hope it helps! Please note that the actual AP with this item build is over 700 thanks to Rabadon's Deathcap.
This part is what I think that matters the most. This item sequence was made to battle a team that has mages and magic resist. So i will give you some choices:
If you have a bad start and it's kind of hard getting kills you should buy the Deathfire Grasp instead of the Mejai's Soulstealer.
In case the other team does not rely on AP as well, you could change the Abyssal Scepter with Rod of Ages. The Rod of Ages gives you 450 health instead of 57 magic resistance.
Finaly, if the enemy does not have magic resistance you could buy Lich Bane instead of the Void Staff, thus being able to destroy towers more easely.
Sorry if this guide isn't helpful enough, but I will try to update it as soon as posible. Please leave some comments. If you have any sugestions please leave them below, I really want to know how to make this build better! Thanks for reading!!