"Best" is subjective. A really good definitition of best is, the ammo that functions the most reliably in your particular gun.
25-350 USD or so
.223 Calibre although .223 Will fit on a 5.65 mm, a 5.65 mm Will not fit in a .223 calibre chamber.
buffaloarms.com
There are various types of ammunition. There are also particular guns that use the recently developed 30 mm ammunition. Among them are aircraft guns and armoured vehicle guns.
.30 caliber.
6.8mm / .270
100-400 USD or so
If the barrel has 5.56 printed on it or you have verified with the manufacturer that ALL of their barrels are good for 5.56 ammunition.
7.65 = .32 ACP
A 30-06 in MM is a 7.62x61 round. Also considered a 30 cal.
ATK Small Caliber Systems is the world's leading producer of high-quality ammunition and links for the military in 5.56 mm, 7.62 mm and .50-caliber rounds.
Depends on what type of 32 ammunition you are referring to.