The best way to go is to buy popular non-expensive items based on when you plan to be able to buy your scarf, you always keep your gold locked away in items when your on larger quests.. this will keep inflation from damaging your quest [such as the NM Scarf increasing another 100k and you needing to get that, if you have other items bought then they will also inflate and that will work to counter the inflation of the NM Scarf.. perhaps even surpass it!].
Choosing your investments:
Lets say you plan to have your scarf in two months, your probably going to want to try to invest in smaller items so they can rise smoothly and you can still sell them easily.
But if you planned to have your scarf in 4 months you might want to try and get a ninja headband, kiki kitty, and penguin slippers [ex.] so that they will have a big jump or two over those 4 months... and wont be a large quantity of items to sell.
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Be sure to invest in the items you think will increase before the end of your quest, because a bunch of bought investments are worthless if they wont pan out before you have the gold to buy the NM Scarf.. or before the NM Scarf makes its big jump.
[I am a credible resource because I was able to get the NM Scarf in a manner of 2 months this way, when the item was priced at 560k] ^.^
~I'd like to hear other peoples opinions though~
