You'll almost certainly spend more on HQ pelts, mana vials, and other materials to get your tailoring into the 120s than you'd have spent just buying a full set of Wu's in the first place.
But, you said you want to farm all the materials yourself. Okay, let's look at the math: it'll take around 5 combines to get a skill-up (probably more if you have low WIS/INT, which you will as a Monk). You start on reinforced armor around level 60 and it doesn't trivial until 108. How long will it take you to farm ~250 HQ pelts? Then you can start on attempting Wu's, which is even more expensive to make.
My advice: farm whatever sells well, save up for a set of Wu's. Make your own cured silk in the meantime if you want; that will serve you just fine until you can save the 450pp or so.
And don't forget to buy weapons.
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