Noob question: How can I craft item for merciless, like tri-res item?

As title, I see a lot of item that have 2 res or tri-res, which is undoubtly useful for merciless and endgame run. I have unidentified uncountable items but see no tri-res or so, so i guess it is crafting.

Give me advices!

Moreover, if you guys know any useful topic about crafting just link it in here. I am really appreciate that.

the missing resist, you can get by leveling the Master: Haku. take his crafting bench and put it in your hideout.

another way is to use an exalted orb, but you will not be sure if you will get resist.

This is the most useful thing to have when considering item affixes/mods or crafting, among many other things:

http://pathofexile.gamepedia.com/Item_Affix#mw-mf-search

The best way to acquire gear is to buy it from other players. Crafting with orbs is expensive, so unless you have a lot of them, it won't be easy. However, now with Forsaken Masters, you can craft a mid-range mod onto an item for much cheaper, by using a master's crafting bench.

Trading and crafting through masters are the best ways to acquire gear for most players (and you can even combine these by buying an item and then crafting a mod you want onto it, which is one reason why the above link is useful). While you might not get lucky and get the tri-resist gear you want to drop, chances are someone else will. And they'll sell it to you.

You can always craft with orbs as well, if you're looking for the very best gear and have a lot of orbs (the orbs are very expensive, like Exalted Orbs, but they also can roll the highest level mods). However, if you have a lot of orbs you can probably just buy the gear, once again.

For finding items you want, in terms of trading with other players, this site is helpful: http://poe.xyz.is/

Trading is usually the best way to acquire gear. The masters are very useful as well.