Tips resarcana

Basic Strategy

Don't put too many artifacts into play. Putting 4 or above is usually a bad idea.
Don't think the game is all about the essences. They are useless unless you can convert them into points.
You should discard cards you don't need to get essences you want to play better cards.
Get a place of power early--their powers can aid you to victory.
Don't afraid to pass early if it can give you a magic item that you want.
Dragons are not good ideas, but if it can break your opponents' plans, that will be hell to them! To counter, just keep some life, and in 4 player games you should expect at least 1 dragon. Dragons can also score with Dragon's Lair or Sorcerer's Bestiary.

Alchemy: Not an effective exchange. Only use it when you really need that 2 gold, e.g. buying a mounment or place of power.
Collecters (calm/elan, death/life): Good in first turn if you want to buy a place of power or a good artifact.
Divination: Usually of no use, as you gain nothing. However, you can use it to cycle out useless cards with cards you want.
Protection: Usually of no use as attacks and dragons are not common. But if you notice potential attacks that may break your plans, grab it.
Reanimate: Very useful when you have a matching artifact or place of power. However everyone wants it, so get it before your opponents.
Research: Basically, it is exchanging 1 essence for 2 essences or 1 gold. You can use it to dig for a card, but Divination is better for this. Or you can play it if necessary, therefore it is worth about 2 essences.
Transmutation: Offen of no use as the game provides lots of methods to exchange essences. However, if you have none of them, try this.

Alchemist: First ability same as Alchemy, second worse than collecting. Hmm...
Artificer: Not obvious, but the discount is useful. Especially when you need to play useful cards for combos.
Druid: Quite powerless, but with Mermaid or Sacred Grove I may change this opinion. Worst of all mages I guess.
Duelist: It is nearly 2 essences per turn if you have a death--known to be strong, as other mages mostly produce 1 essences per turn.
Healer: Hard to win because no combos with other cards. But in 4-player games, it can save your game in some occations.
Necromancer: Not the best, but good with Catacombs. Why? You can discard a card for 2 life and change to 3 death.
Scholar: Same as Research, but Research is what everyone wants. Imagine you have access to one yourself.
Seer: Seems useless, but with Dragon's Lair it's choose 1 from 5 mounments each time. Or you can search for that card you really want.
Transmuter: Better than normal transmutation, because you gain an extra energy. But there are actually many methods to change essences...
Witch: This is deadly! I have seen lots of people winning with witch's reanimate ability. Best with Catacombs of the Dead or Dragon's Lair.

Chalice of Fire: The collecting ability pays off in turn 4 even if you don't use it, and its reanimate is useful with many places of power.
Chalice of Life: This strong essence generator feeds itself and doesn't need to be turned. Best with Sunken Reef.
Corrupt Altar: Expensive, but you can play expensive cards, use it once then sarifice it. If you are tired, just sarifice the Altar itself.
Crypt: You can discard a card then resurrect it with a discount. Crazy with a sacrifice card. Don't need it? Then get 2 death instead.
Dragon Teeth: Feeds itself and discounts you on dragons. Although bad with places of power, it is best with Philospher's Stone to get gold.
Horn of Plenty: Much above average. Pays itself off with 2 turns. Fits itself into any strategy. First pick in nearly all draft.
Mermaid: You can use mermaid to score while using other abilities of places of power. Better then a novice would think.
Vault: It's cheap, it's flexable, it can be aimed for small or big! Good with both gold and essence strategies.

Bone/Fire/Water Dragon: Expensive, but easy to dodge. Better to discard for essences.
Dancing Sword: Its collecting ability only pays at turn 4, and if your opponents see this, they won't play dragons and makes this useless.
Elemental Spring: The cost is steep, and after 3 turns it is just 0. Most attacks can be prevented by an essence, so this is redundant.
Hand of Glory: Your only gain is just 1 death, making it even in 4 turns. Only slightly better if the cost is mitigated.
Windup Man: Worst card in the game. The cost is high, and it is slow to pay off. While you are waiting, the engine is dead and you have spent a bunch of essences for nothing.

Colossus: Worse than Solomon's Mine, as it gives 3 gold for 3 essence instead of 4 free gold.
Golden Statue: If you don't have extra gold, it is useless. Otherwise, it is 4vp with a discount.
Great Pyramid: Don't buy it on round 1. However, it is game-changing in later rounds.
Hanging Gardens: The stronger the earlier bought. Excellent on round 1, but expensive on later rounds.
Library: Better than Solomon's Mine in terms of flexibility. However, it takes more actions. Best to buy early.
Mausoleum: Good with Places of Power that needs death. Also, it is a staller to prevent your opponent from getting your magic item.
Obelisk: Good at anytime in the game. If early it can help you to buy a Place of Power. If late it can give essences to dump on them.
Oracle: Fits well into a mounment strategy. Grab it early to provide more choices for the other 2-3 mounments you are going to buy.
Solomon's Mine: On turn 1 it is a free point. Later it can let to buy more mounments instead of wasting your 3 gold, so buy it early.
Temple: Decent if someone has a dragon, otherwise it is average.

Alchemist Tower: It can be bought on turn 1, and although there is no turning abilities, it can be used for a turn 4 victory with good cards.
Catatombs of the Dead: Overpowered. With Chalice of Fire (and Witch/Reanimate) you can get 2-4 points per turn, plus death from discards.
Coral Castle: Purely 3 points. Fine, but without other places of power you cannot win.
Cursed Forge: Unlike other cards, this partially hinders you. However, it can be defensive with Mermaid.
Dragon's Lair: Also overpowered, although you need to discard all of your cards to play this. With reanimates you can buy tons of mounments.
Dwarven Mines: It is 3 essences for 1 point once per turn. Or you can use the 3 gold ability to buy a mounment each turn. Plus it is cheap.
Sacred Grove: Sounds useless but you can convert all calm to life then to gold with Philospher's Stone. That would be a massive blow!
Sacrificial Pit: It's ok, but if you have a lot of creatures and dragons you can use the second power to gain gold. Good with Dragon Teeth.
Sorcerer's Bestiary: It's tricky, as you need to have a lot of energy to steal dragons. Better to have a dragon strategy.
Sunken Reef: The most effective point-gaining place of power. Plus it has unlimited use. Some people use this to get 10 points in round 4.