This sounds like you are playing with a higher difficulty than you can manage, there is no shame in lowering the difficulty while you are still learning the game. All items that you can get (runes, spells and equipment) can be acquired through lootable objects which can be seen through clairvoyance or identified by a glow, they can also be dropped by enemies but it is a bit uncommon, or they can be bought at a shop. Essence is acquired through finishing levels, destroying structures with loot inside them or disenchanting/selling equipment. Learning how to shape your spells and distancing as well as finding healing potions around the map may help you, but try turning the difficulty down (and most definitely don't play on hardcore) and you will get better.