For the clothing industry silk is by far the easiest, as you will need only a loom and a clothier's shop next to each other, with a cloth stockpile somewhere nearby. This is a very simple set up; your weaver will run to the nearest spider web, instantly turn it into thread, and bring the thread back to the loom to weave into cloth. The cloth you make will almost always be worth more than cloth you buy from traders, as the cloth you can buy doesn't have any quality modifiers. Just place a cloth stockpile close to your clothier's shop, and you're set.
If you use rope reeds or pig tails, or if you want to dye your cloth, things get a bit more complicated. For plant threads, you need a farm to grow them, a plant stockpile for the result, a farmer's workshop to extract the threads and a stockpile for the threads so your weavers can have ready access to the raw materials. For dyes you need a quern instead of a farmer's workshop and a plentiful supply of bags to hold the dye, and then a dyer's workshop to dye the cloth or thread(It doesn't matter if you dye the thread before it's woven into cloth or after). Once again, dying your own cloth will be much more valuable than buying dyed threads from traders, due to the quality modifiers.
Leatherworking is somewhere between silk and plant fiber cloth in terms of difficulty. You need a butcher's shop and a nearby tannery, which I generally have adjacent and have one dwarf do both jobs. You need a refuse stockpile nearby that is set to only accept corpses, as butchers will only butcher nearby things. You also need a source of animals, either from hunting or ranching or just butchering what your military kills. Once the leather is tanned just place it in a stockpile close to your leatherworks. Unlike cloth, leather doesn't have quality modifiers, so it can be extremely worthwhile to purchase some or even all of your leather from traders.