Padded shorts are a must for me.
A proper pair of riding shorts. I have Endura Singletracks
On top I have a long sleeve baselayer, then either a Rab softshell or a Mavic Gore-Tex jacket. The water proof I am slightly unimpressed with as it is not very breathable. I stayed drier and at a more stable temperature in my softshell.
Come summer I normally go with a thin long sleeve baselayer or compression top for some wicking action with a standard short sleeve t-shirt on top.