Everyone is different in how they deal with cold on a ride, but here's how I do it (copy-n-paste):

The usual dress is bibs/shorts, jersey, cycling shoes, coolmax-type socks, helmet, sunglasses and half-finger gloves. As the temps drop and depending on whether it is sunny, cloudy and/or windy, here’s what I put on:

• @ ~ 60º F – arm and/or leg or knee warmers, add short sleeve thin base layer under short-sleeve jersey.
• @ ~ 55º F - switch to a mid-weight thermal long sleeve jersey and switch to mid-weight thermal tights
• @ ~ 50º F – switch to a long-sleeve thin base-layer, switch to a thicker wool sock, add glove liner under half-finger gloves and add a headband to cover my ears.
• @ ~ 45º F - add toe covers, switch to a skull-cap.
• @ ~ 40º F – add a thin packable-type wind resistant jacket, and add a windproof gloves or switch to a windproof insulated gloves.
• @ ~ 35º F - switch to a thicker base layer top, add a silk-weight base layer tight, add a sock layer and switch to wind booties.
• @ ~ 30º F and below – switch to windproof thermal jacket, add balaclava, switch to a thicker mid-weight base layer tight or switch to a thermal tight with windproof panels, switch to ski gloves and switch to sunglasses with a larger ‘shield’.
• @ ~ 25º F – switch to ski goggles, add a silk-weight base tight, switch to neoprene booties, add a windproof/waterproof helmet cover.
• @20º F or if it snows – I switch to rollers inside.