My riding buddy and I tend to be about the same in these situations. Meaning, we wear the same layers of things, and both try to go lighter and tolerate the cold when it seems realistic.

Having said that, 45 is pretty nippy!

In that case this would likely be our ensemble: Regular cycling kit, of course. (Shorts and jersey). Arm warmers for sure. And either leg warmers or full "tights" over the shorts. (Whatever cycling shorts are made out of, those in pants form with no padding.) We both have long ones and shorter ones. In this situation, we might got for the shorter ones that go just below the knee. And we might be fine to just leave them on all day if the temp only gets to mid 70's. Typically if we wear the "pants", the hope is that they'll stay on so we don't' have to figure out what to do with them. Once or twice I have tied mine in a big knot to my tube! However, we find we typically don't get overly hot in them when the temp rises.

I did eventually start wearing leg warmers more. I didn't wear them for a long time cause they can look ridiculous on me with the elastic forcing my thigh fat to stick out in a big bulge! They are definitely more handy to pull off and stick in a pocket when necessary, though.

We also would wear a vest over our jersey. This bunches up super small to shove in a pocket.

My friend might wear full finger gloves, but I never do no matter how cold it is. I wear fingerless gloves and don't feel that full finger gloves necessarily help any. Plus, I'm always reaching for tissue and blowing my drippy nose, and can't feel the tissue with full finger gloves.

When it's in about the mid 50's is when we get brave and don't wear anything extra, except "maybe" arm warmers. That is on a long ride when we know the temp will rise (as will our body temp from riding). We find that the first ten minutes is pretty miserable, but then you don't even notice it anymore if you're riding at a good pace to warm your body.