Does it matter what size circuit breaker I use for lights or recptacles 15 or 20?

14 AWG or 12 AWG wire can be protected by a 15 A breaker.

14 AWG wire MUST be protected by a 15 A breaker.

15 A outlets can be used on a 20 A circuit

20 A outlets may only be used on a 20 A circuit

12 AWG is more expensive than 14 AWG

20 A outlets are more expensive than 15 A outlets.

At 120 V; P (watts) = 120 * Current

Suggest 3 conductor w/ground for switch loops. Allows timers and automation devices that require a neutral.

15 amps using #14 wire should be enough, if you move up to 20 amps you need #12 wire and 20 amp breaker