Depends, if I'm just going out to ride, even if its a training ride I just wear shorts and a shirt, if its colder I've got leg warmers that go from the shorts to the ankle and a tighter fitting hoodie to wear. If its cold, or colder and I'm heading out for more then 30 miles I put on cycling shorts underneath with tights over and then shorts, cold days will include leg warmers under the tights and a long sleeve wool shirt under the t-shirt with a hoodie on top.
MTBing I wear shorts as well unless its a longer day then I have padded mtb shorts that are baggier and a t-shirt.
If racing then I do a cycling shorts and a tighter fitting shirt.
I haven't bought a new jersey since pre-kids days when I could fit an xl easily and even a large depending on fit. Now I've tried a couple of XXL and they were a little tighter then I'd like though I still fit xl shorts as I'm more of a muffin top, easily fit large pre-kids. I'm going to buy a couple of pairs of bib shorts this year since I hear they do a little slimming of the top which with a little weight loss should squeeze me into an XXL top I hope. Still only wear the jersey and shorts though when racing. One, I'm a little body conscious, two I've always just felt comfortable in khaki and cargo shorts; I don't find them too hot nor do I worry about aerodynamics when just riding and training, just means I can go faster when I'm racing, and three I'm too cheap to buy that much cycling clothing. Already spend enough on it for the wife and kids. Haven't worn jeans or jean shorts in 25 years since I was a teen, just always found them too tight and hot.