Tried this build and it didn't work for me. :(

DigDug's build is great though. This build is too squishy I can't even push back a wave of creeps at level 18! I think it's too micro intensive in order for it to work, and don't even think of initiating a fight with this build. In team fights, I had to rely on sheer luck that the other team doesn't notice me, I was able to gain some kills but mostly due to luck. Got 7/11/3 with my first use of this build and we lost.

Am I just playing it wrong? Maybe you should add a more detailed strategy guide.

I agree. Tried it and magic pen is better (masteries). Still, I don't have enough IP for magic pen and I play mostly Poppy and mages, so AP works fine for me. Well, everytime I play Poppy I go AP and most of the time people are laughing for the first few mins of the game, and later on when I get some doubles or triples and crit for 1.5 late game I'm the one who's laugning ;p + I try to avoid playing champs the obvious way, it's more fun and it makes people think about what the F am I doing so it gives me an element of surprise.

I've actually been thinking about trying this type of thing out myself, but haven't gotten around to it. I would recommend going for Magic Pen runes instead of AP runes though. Also rather than the mastery for ignite I'd go for the magic pen mastery as well.