I got to around 100 in tailoring and 95 in jewelling, so I'm no genius when it comes to crafting, this is just me sharing my experience and thought when I started to craft in GW2.
A warning to anyone who's interested in crafting is that you should be prepared that you are going to have to spend coins in order to level up your crafting. Although I used everything I came across and saved everything that could be use in crafting, I found myself often needed to buy things on the auction house to get further in my crafting professions.
Short guide to crafting in Guild Wars 2.In the beginning crafting in GW2 looked like in any other MMORPG. It has a base material (e.g. copper) that can be refined into ingots, that you can later craft something with.
To create a dagger for example you then need to create a blade and a handle, and then assemble them.
However, you notice pretty quickly that something more is required in order to continue to gain crafting levels, when around crafting level 30 it starts to require extremely high numbers of material to increase the level.
Experimental ModeInstead of putting together the blade and handle of a dagger directly you go into experimental mode, add the handle, the blade, and then an optional crafting materials (often stuff that drops from mobs, such as chlorine, bits of gems, vials of blood, etc. etc.).
In doing so, we add a magical component and gives its item a bonus. First time to test a certain combination you get extra exp and can often jump 3-4 level up if it is a little more complicated item you created.
When you have created a combination will the recipe be unlocked and added to, among the other recipes, but it will not longer give as much exp.
Therefore it is recommended to start using the experimental feature as soon as possible (often requires level 25 and then 50 for many combinations) to avoid having to spend hundreds of coins for a few levels.
If you have 100 of the base material (eg copper) it is usually enough to refine those to get to approximately level 20-25 so start with that, especially when you stop getting exp pretty quickly for easy recipes (such as copper ingots).
It works very similar for all the different crafting professions, only materials differ between the various crafts.
It is worth to consider is also that you always get exp when you craft, but you can however do sort of like critical hits in crafting that gives you bonus exp. So it's a bit of a gamble, but you can not fail to craft anything and thus wasting material, so you always get something out of crafting.
Things you create in crafting is also quite usable, when I was at level 28 (normal level), I could at level 90 (crafting level) create gear that was better than any I've had in rewards / drops until then.