where do you get essence from other than buying it? how often does it come up in battle?

also do you have to buy traps and how do they work??

You can get essences in mission satchels, nurturing, jinxie's jamboree and battling. It is very rare to get a essence from battling, (like maybe 5% or less) and it's even rarer to get one from nurturing. You can nurture 1000 eggs and not get one essence at all. (So maybe a 1% or less chance).

If you play jinxie's jamboree and get 3 lamps light up, you get to play the bonus game where out of about 30-40 choices, there is one essence (and other items) available.

Hope this helps

For your question about traps, yes you do have to buy them (though Jinxie will give you 3 of them for the pet capturing quest).

When you're in battle and see a pet you'd like to capture, you go into your battle inventory (see the little satchel in the bottom corner of your battle screen?) From there you click on the trap you want to use, and then select the pet you want to use it on. The trap will be used at the very start of the next turn, and so you'll see in the battle log the results. The trap can either be successful, fail, or the pet can run away. If it fails you'll still have another chance the next turn, but if the pet runs away it's gone for good.

Also, make sure you pay attention to what type of trap you're using. Some pets can only be caught with higher level traps (Such as rare and epic pets).