Have no fear, only gear.

Rule #1: Cotton is the enemy. It holds smell, sweat, and doesn't wick away moisture like athletic synthetics. Trust the scientists who engineered those fabrics; it's their job.

Rule #2: Buy one pair of nice socks, you will always reach for them.

Rule #3: You are rarely too cold, 45 degrees? Light layers. 55 with sun? Short sleeves! Anything over 70? Shorts/Tank/No rules!/the purge! (NYC winter talking)

Rule #4: Any running done at dusk or twilight requires donning neons, safety first!

Rule #5: Ipod arm bands are amazing.

Rule #6: Any run under 5 miles shouldn't require carrying a water belt/ bottle. (Plan to run through parks/ plant a bottle in a secret place)

Rule #7: Sunscreen.

Rule #8: You never need to wear two sports bras, find a supportive speciality sports bra (try Moving Comfort).

To be honest, the most important gear is your sneakers. However, here is a quick list of basic, all season pieces: (Based on my female wardrobe)
-Quarter zip
-Vest
-Tank Top
-Long sleeve
-Shorts with pocket in the back
-Warm long tights
-Light long tights
-Socks
-Sports bra (Am I right ladies?)