tiamat has 2 nice items to start the game with, rejuv bead and farie charm.
450 gold for: 7 damage, 7 health regen, 1 mana regen, spash damage.
considering the price of the components, the stats are actually worth the 450 gold. without the splash damage.
is it a great item? no. is it a "waste of money"? no. could you buy better? yes.
it is a decent first item to go for. you can start with health and mana regen, and pick up some damage along the way.
i like tiamat on sivir. the bouncing blades DO NOT recieve the proc effect, but she makes decent use of the regen and damage it gives.