It is a matter of chance. I have updated the item sell value so that it more accurately matches the sell value of the gems that item would give. However, if you by chance get MAX gems out of a bunch of items, the gems will likely be worth more.
A note for those starting out, your constitution does not get trained later on in the gym, so you might consider putting more points into it. Also your self heal spell is percentage based, so you get more bang out of that if your con is higher.
Demon with ice set is OP. Get a decent crit rate and you just spam ice shards after one hit. Your passive gives you mana back, so you can shoot more shards, the shards kill things, gives you mana. FOREVER!
'Cut Out' spell is easily your most important early on. Spend points on lowering it's cost, raising your mana pool, and get the upgrade that gives you money back when you cut trees. You will win all the levels.
 "Tap Adventure")
 "Kittens Game")
 "Idle Raiders")
 "Woodclicker")
 "DPS Idle"){kind=icon}
 "Castaway 2")
 "Hack Slash Crawl")
 "StrikeForce Kitty")
 "Thrones of Fantasy")
 "Epic Creature Hunter I")
 "Disaster Will Strike 3")
 "Mighty Knight")
 "Loot Heroes")
 "Feudalism III")
 "Cursed Treasure 2"){kind=icon}
 "Bubble Tanks 3")
 "Medieval Wars")
 "Deadly Neighbours")
 "Project Wasteland 0")
 "Robot Wants Ice Cream")
It is a matter of chance. I have updated the item sell value so that it more accurately matches the sell value of the gems that item would give. However, if you by chance get MAX gems out of a bunch of items, the gems will likely be worth more.