"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
The equivalent of 5.65 mm ammunition is .22 caliber ammunition.
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.
100-400 USD or so
6.8mm / .270
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
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.
A 30-06 in MM is a 7.62x61 round. Also considered a 30 cal.
Depends on what type of 32 ammunition you are referring to.