Tires - can wrap them in electrical tape. won't last long, but it's a quick and cheap way to make those VTA tires work a bit better for drifting.
HPI make some reasonably priced shells with light buckets. I know their Gallardo shell had light buckets, but they aren't licensed to make Lambo shells anymore. Not sure which other ones might have buckets. At a glance, the Maclaren F1 shell comes with buckets. Take a look here. http://www.hpiracing.com/hpibodies/200mm/
The 200mm bodies will fit better with VTA tires (The tires you currently have, I believe)
Most touring car slicks and drift tires will look better with 190mm bodies (unless they are mounted on offset rims).
Tamiya make a ton of shells with light buckets, but they are a bit expensive.
smaller spur/larger pinion will increase the top speed a little, but will make the motor run hotter, so you need to be careful.
Hope that helps you a little. Welcome to the hobby and to this forum.