Crafting.

I've never crafted anything in this game before and i recently found out that you can get the best gear for your profession via crafting. But there is a few things I'd like to ask:

1.Is it very expensive?

2.are the materials hard to get?

3.Can you only get certain materials via dungeons, fractals, and raids?

There's lots wrapped up in your questions, but I'll take a general stab at them:

1. http://gw2crafts.net/ will give you an idea of the costs along with a guide to level up each profession
2. Most of the typical ingredients (wood, metal, and the things that drop from mobs like claws an fangs) are reasonably common. There are outliers that are quite rare (maguuma lily or essence of light, for example), but these tend to be for rather specialized gear stats or really narrow purposes (usually guild decorations, which you don't need to worry about). You'll be able to farm or easily buy anything you need.
3. Yes, but again they tend to be specialized. For general purpose stuff like weapons, armor, and food you don't need to do dungeons, fractals, or raids. The materials tend to be either guild hall decoration related or, in the case of fractals, intended to help you improve your gear to do higher tier fractals.

Ascended gear (the best you can get) is expensive, especially if you need to level up crafting first. But you don't need to pay the cost all at once, you can do it a bit at a time as and when you have gold/materials. Also unless you've been selling them all you should have at least some materials already.

Certain items do need materials from dungeons or fractals, and possibly from raids, but they're the exception. You can craft a full set of ascended equipment without any of those. (But you also won't need ascended equipment unless you're doing raids or fractals.)

One piece of advice before you start: Unless you're planning to eventually level all the crafts check which ones you actually need.

• Tailor makes light armour.
• Leatherworker makes medium armour.
• Armorsmith makes heavy armour.
• Artificer make Staffs, focuses, scepters and tridents.
• Huntsman makes bows, rifles and pistols, harpoon guns, torches and warhorns.
• Weaponsmith makes swords, daggers, axes, hammers, spears and shields.
• Jewellers make trinkets - but only to exotic, you cannot craft ascended trinkets.
• Chefs make food.

Every character can have two active crafting professions at a time. You can swap which ones are active without losing progress by speaking to one of the craft masters, or you can buy an item from the gem store which allows you to have more than 2 active. Or you can learn two crafts per character and use multiple characters.

However you do it I recommend taking some time to think about which crafts you want to learn first and making sure they're actually useful for you.

The end-game usable armor types are exotic, ascended, and legendary.

I've crafted some basic exotic viper's gear for myself, and yes - it was pretty expensive. First there's the mere process of getting your crafting skill high enough to craft exotic armor. That alone costs a fair amount of gold. You can just Google "guild wars 2 tailoring guide" or whatever and you'll easily find a guide that walks you through the quickest way to level up the skill. But you'll be buying a lot of stuff off the auction house in bulk and it'll cost ya.

Then the exotic armor itself costs so much in materials that you're almost better off just buying the exotic armor off the auction house. I only crafted mine because you can't get Viper's stats off the auction house. And it cost a fairly hefty sum.

Ascended armor is better, and it costs a lot more to craft. You can buy components off the Auction House or craft them yourself - either way is pricey. I had fun crafting my own ascended staff and scepter, but it definitely drained my bank account. Legendaries are even more expensive than that from all I've heard - though I've never crafted any.

Keep in mind though, you can run most of the content, and even raid adequately in just exotic armor and maybe a couple easily acquired ascended accessories or an ascended weapon. So you don't have to shoot for legendary right away. Just try crafting some exotic stuff for starters and see how you like it.