Ive made a spreadsheet cause Ive found myself often baffled how does my items improve my gameplay mathwise.
There are lots of predefined stuff to see the larger picture, you can choose wheter you have Abyssal Scepter or not and you can input your spells dmg, ap and ap ratio to check how much dmg youll do after all the processes.
% M pen is applied too, in 15% (Archaic Knowledge) and 49% (AK + Void Staff) forms.
Ive made those spreadsheets in Excel 2010 but in zip file there are 2 versions, 2003 and 2010 excels if someone doest have the newest version.
Enjoy and feel free to leave some feedback.