The absolute best/fastest is to have a high level alt or friend mailing you white/green/blue items they gather while questing. Intricate items do offer more inspiration to deconstruct than the same quality/level item otherwise would, but obviously if the markup is for more than the amount of extra inspiration then don't go that route

You can get your own intricate items by doing the daily writs, but if you're only a low level blacksmith the intricate item of a low level will still give less inspiration than a high level item without intricate qualities likely would. You get more inspiration with items of higher levels, items of higher quality, and intricate items but the amount you get is capped based on your current blacksmith level (so if you're blacksmith level 5 for example don't buy top level gear to breakdown). The deconstruction inspiration cap seems to no longer apply much to white/green items somewhere around blacksmith level 20 although I can't give you exact rates/details on that at this time (I just remember on the most recent alt that I've done it with that the inspiration amount stopped jumping so much as she leveled blacksmith around that time).