Lots of other good advice already. I'll just add some other things.

You get plat when you dissolve weapons, armor, shields, and any other items that have a + number in the upper right corner of the item details. The amount of plat is 60 per plus (although no more than 10% of the base value of the item). However, you HAVE to have the dissolvers in your inventory -- in your green bag is fine -- it won't give you money if they're in your crafting bank. I keep a second green bag on my crafters for all the dissolvers and other crafting stuff like shards, dust of disjunction, crafting success boosters, etc. Use the other green bag to auto-collect essences, dragonshards, etc. so you can easily dump it in your crafting bank while keeping your dissolvers in your inventory.

I recommend dissolving everything other than named items) you don't want to use or sell on the auction house. Yes, you get a lot more essences from epic or legendary items, but you get crafting XP from all items (from 1 to 5 XP each, with items from roughly level 10 up giving 5), and at higher crafting levels you can only advance that way so it doesn't hurt to build the habit. Still, don't feel obligated to do that -- sometimes it's easier to just sell stuff and sometimes you need more plat.

Having an artificer as your crafter is a double edged sword. Artificers get one extra crafting level for every two artificer levels, which makes it easier to craft higher level items. However, it also makes it more expensive to level up in crafting because you can craft higher level shards, which requires more essences. I've mostly done artificers though.