League-of-legends – How to change the color of turrets on the mini-map

Don't worry too much about trying to get kills - Alistar's role in a match is to provide support and disruption. You may not get many killing blows, but if you're a decent player, you should have many many assists instead.

If you're worried about losing out on the money that comes with kills, I'd suggest you look into Gold/10 items on Alistar - Philosopher's Stone and Heart of Gold being the better of the 4 for him. (Duplicate items don't stack, but there's nothing stopping you from picking up one of each).

That said, Alistar makes good use of Sheen, which is a cheap way to double your basic attack damage, and gives him mana to boot.

What you are looking at is most likely the particle effect for the active of the Shard of True Ice. This is the only image I could find on the Internet, but I believe the particle effect gets more detailed.

The active effect for the Shard of True Ice slows all enemies near your (allied) target by 30%. This effect lasts for 4 seconds. Common targets include tanks/initiators (to keep enemy teams from disengaging) and carries (to keep them alive if your team disengaging).

The Shard of True Ice builds out of a Kage's Lucky Pick, Mana Manipulator, and 535 gold.