CASH COW!
Tailoring is very easy to GM, it will take you one or two days tops.

Firstly, start off with 50 tailoring and 50 of whatever else (magery helps so you can recall from shop to shop). Use the 1k gold you start with to buy yarn in Trinsic or any other cheap town. Spin all this into cloth, cut it up (IMPORTANT: Don't cut the cloth into bandaids! I made this mistake several times, and it is a hassle), and then buy a bunch of extra sewing kits. Start making cloaks with the cloth you have until you can make robes (so about 55 skill). Make sure to sell the items back to the store for profit that can be used to buy more yarn. Robes will take you to 75, at which point you can start to make oil clothes.

This is where it gets cheaper.

Oil clothes only use 1 cloth, and gains are fast, so you will probably need somewhere between 3k-4k cloth to get to 99.6. Unfortunately you cannot sell cloth, but it uses so little resources it doesn't matter too much. If you want, you can pick cotton with an alternate character so you don't use money buying yarn. It's helpful to run an organizer agent if you're just going to macro, so all the oilclothes go to your bank (macro in the Razor section).

Once you hit 99.6 tailoring, you'll need to start making studded leather tunics to gain. You will need approximately 500-600 leather for this, so go to Delucia or any place with harts/bulls/llamas/horses, and kill and skin them for leather.

You're now a GM tailor.

A tip for bulk order deeds - only sell one item at atime! It's random when you get one, it's not based off how much you sell at once or anything like that. You can get it your first time or your fifth time. The cheapest thing to do is to sell individual bandanas.

So, in summary:
50-55 CLOAKS
55-75 ROBES
75-99.6 OIL CLOTH
99.6-100 STUDDED LEATHER TUNICS