Layette on the registry, clothing size question

MWmom2BB1

So I know it's a good idea to have some clothing on the registry.  Mostly I'm seeing 4-8 bodysuits long and short sleeved, 1-2 wearable blankets, 2-4 gowns, 4-8 footies, 4-6 tees, and 4-8 pairs of pants.  My question is what size should all this stuff be?  Should I register for a mixture of sizes?  How fast do they grow out of the 0-3 or 3-6? Do i bother with newborn sizes or just maybe have an outfit or two?