Carbide.....good carbide. It's not all created equal, and bits in general are not created equal...since they spin in excess of 20K rpms, buy the best quality you can and avoid the off-name super cheap stuff. Buy 1/2" shank whenever possible if your router accepts them. For the bits you'll use most, IMO it's better to buy a few good quality bits, than several dozen low quality bits. You can add specialty profiles as needed.
MCLS, Woodline, and Grizzly are my bargain suggestions. Price Cutter and Katana are a step up for a little more money.
Whiteside,
Infinity, Eagle America, Freud, and Amana are top shelf...some offer small sets of the most commonly used profiles in the $100 range, which make them a little more affordable than buying all bits individually.