I don't like the idea of items in this TS, save it for SC2 methinks. The main problem is that by nature, anything you can make an item do you can make a spell do, so this will inevitably lead to overpowering and overlapping by combining spells and items. To differentiate them, items and spells should do totally different things. SC2's editor will allow this wider degree of effects that can't really be done now.
Still, I have ideas. For items, some have three classifications - Lesser, Greater, Perfect. From Lesser to Perfect versions, they cost more and are more powerful. For items that have this classification, I'll say "LGP Item" and show the effects each level has.
Name: LGP Potion of Healing
Effect: Restore health to 50%/100%/150% of max HP
Cost: 50/100/150 Minerals
Extra: One-use
Name: LGP Potion of Magic
Effect: Restore Mana by 50/100/Max points
Cost: 50/100/150 Minerals
Extra: One-use
Name: LGP Anti-Magic Cloak
Effect: Lesser Cloak makes you immune to Level 2 and lower spells. Greater makes you immune to 3 and below, Perfect makes you immune to all spells. All cloaks are temporary
Cost: 50/100/200 Minerals
Extra: One-use
Name: Goblin/Water Gremlin/Ice Gremlin Gem of Summoning
Effect: Summon a Goblin, Marine or Zealot for the player to control until it dies
Cost: 25/50/75 Minerals
Extra: One-use
Name: Potion of Restoration
Effect: Remove effects of spells from yourself
Cost: 50 Minerals
Extra: One-use
Name: All-Seeing Eye
Effect: See the entire map for a period of time.
Cost: 50 Minerals
Extra: One-use
Name: Smoke Bomb
Effect: Disable the sight of a nearby enemy for a period of time
Cost: 50 Minerals
Extra: One-use
Name: Sensor Probe
Effect: Create an invincible Observer the user can move about for a period of time.
Cost: 75 Minerals
Extra: One-use
Name: Mirror of Deceit
Effect: Spawn a Hallucination of yourself. It will have the same HP as your max.
Cost: 25 Minerals
Extra: One-use
Name: Force Field Generator
Effect: Become invincible for a period of time.
Cost: 75 Minerals
Extra: One-use
None.