Most HSFs for the enthusiast market come with very good TIM either pre-applied or in a separate tube or packet. No need to buy any until the first time you need to reapply it.
Here's a quote from a recent review at benchmarkreviews.com:
"When applying thermal interface material to the Xigmatek HDT-S1283 exposed copper heatpipe 120mm CPU cooler, it's very important to understand that most TIM's used with aluminum coolers will cause oxidation to the copper heatpipes upon contact.
Unfortunately, Xigmatek did not include any special TIM for their exposed copper base, which is an accountable oversight. While nearly any TIM will suffice, it is recommended that you do not use a material based on silicone oxide for best results and product longevity". Seems like the reviews I've read at Benchmark reviews lately have contained slipshod reporting - see the following...
While the review at silentpcreview.com shows that it DOES include a packet of TIM. The product's manual states likewise.
Personally, I'd be leery of any company that didn't supply some TIM.
Another hint for exposed heat pipe HSFs is that there are substantial gaps around the pipes in the aluminum base. Those gaps need to be filled with TIM and not left to allow air pockets above the contact surface of the CPU. Air pockets concentrate the heat. This is contrary to the recommendation of the thinnest possible application which was common on flat based HSFs.
.bh.