The material that drill bits are made of determine their strength and cost. The options include, starting with the least expensive; high-speed steel, black oxide, cobalt, and titanium. In our tests we found the titanium bits to significantly outlast the alternatives, enough so to justify their higher cost.
We especially liked the DEWALT DW1361 Titanium Pilot Point 21-Piece Drill Bit Set. It contained a good variety of sizes and the pilot point significantly reduced the drifting of the tip when first starting to drill.