So I found some Pacman today

At the local. Boy is that stuff expensive.

So, what should I do? I was thinking of slowly building up a big starter, pitching most of it into my next IPA, then continue adding wort to what's left to propagate further.

Ideas?

Since you're concerned with expense, why don't you make a mild beer (of your choosing) and harvest the yeast to four or five vials.

Then make a big IPA with a pound of hops (your choice but at least 1/2 pound in the last 15 minutes of the boil), 13 pounds of Maris Otter and a generous amount (a couple pounds) of Carastan malt. Pacman will eat through that specialty grain and leave it as a really dry, malty backbone to balance out those hops. Ferment low (about 61-63F). Drink it young and send me a bottle.

-Michael