Elemental Scion Weapons

What are some of the best weapons for an elemental scion?

Sadly, "elemental scion" is probably not specific enough for us to give any sort of answer to your question.

Doryani's Catalyst is a good weapon for elemental builds in general.

After that, we probably want to know: Will you use Attacks or Spells? Will you pursue as much crit as you can, some crit, or no crit at all?

Which Skill gem(s) do you plan on using? That often defines a fairly comprehensive set of characteristics for offense (damage) optimization (trying to get the best setup). That is why many people say you must start with the skill gem when theory crafting.

I'm focusing on spell casting. I am investing a lot of points in elemental spell damage passive skills (Cold, Fire, and Lightning). I'm using some crit, but I'm not using a lot.

These are my main gems right now:

Spark
Ice Nova
Fire Storm
Glacial Cascade
Flame blast

I'm trying to find a unique weapon that can buff up my elemental and spell damage.
I have about 18 Chaos orbs right now, and I am level 59.

Okay, that narrows it down a bit.

Spells are generally not as dependent as Attacks on Weapon of choice, which leaves you with more options.

EDIT: This means that gem levels and logical gem links will usually give you much more power than your weapons will.

If I were in your shoes, I would look for a rare wand or dagger with plenty of spell damage (with new wand implicit, 100%+ spell damage should be pretty cheap, I think) and some spell critical strike chance, and take Elemental Overload keystone passive to make use of the some-crit speccing.

Generally, staves (staffs) will probably give you the highest raw power in endgame, but top players prefer daggers so that they can gain defense from the shield slot and use the Whirling Blades skill to move around.

I might just be getting old, but I can't think of any really good uniques that would fit in your price range.

Pledge of Hands would be a powerful staff for spell dps if you could get ahold of a 5L or 6L one, but you probably couldn't get such for less than 20c, more likely costing 40c+. If you don't have a 5L yet, it might be worth buying a 4L Pledge.

Heartbreaker is alright, got some crit and Spell damage, and a couple of unique features, but unless the market collapsed last time I checked, you can get much stronger rares very easily.

Divinarius is an old one, decent spell damage and crit, but it was 1 ex last time I checked. But that was when 1 ex wad worth 20 chaos or so, so obviously a lot of room for price changes since then. It's very likely Divinarius is cheap nowadays, but I'm on mobile so can't check for you.