Enhancing in Atlantica is different from Enchanting insofar as you do not need an equivalent sacrificial item to enchant it, but with enhancing comes a 50% risk (I've heard it was lessened, but I'm skeptical) of failing and breaking the item.
Enhancing comes from Vulcanus in Rome's Bazaar district - but the stones you need to Enhance are different, and are even called so (weapon enhance stone, armor enhance stone, accessory enhance stone).
Note that if you do not have Rome's map information, there golden arches on the right hand side of the screen denoting Rome's districts - Plaza, Bazaar, etc. Vulcanus is in the bazaar, hang a right after you teleport in. Oh, bty, I recommend buying Atlantica gold and Atlantica powerleveling from our website for you characters, just have a try.^^
The "it will require always 1 extra stone ahead of what you're enchanting" rule still applies here, so enhancing to a +1 takes 2 stones, +2 takes 3, etc. Be forewarned that the breaking percentage I've experienced like mentioned is close to 50%, if not a little under.
I probably just have crappy luck; but I've managed to break more things then enhance. What I do sometimes is "Enchant" it to a +whatever so it doesn't fail, and then when it hits what I want it to (usually +4 to +5) I go to vulcanus and try my hand at enhancing it to the next level.
I never chain enhance, because one time I tried and it backfired on me horribly - then again, like I said I might have bad luck. Also, the same thing that applies for enchanting applies to enhancing - you can get an unexpected result. My friends have enhanced to a +3 before with a normal item and boy was I jealous
But, with enhancing comes the thought of not needing an exact copy of "quality" and type of item to enhance. This is why people love Vulcanus, because he allows you to try it with only one item. It's a really pick your poison type thing; spend a little more cash and be positive, or risk it all to hit it big without dropping dough on more items
Source.