30f-55f is the range where waterproof breathable rain jackets like from Showers Pass work pretty well, so that's what I'd wear. They probably also sell long waterproof breathable pants.
Waterproof helmet cover, waterproof gloves, you can wear waterproof shoe covers or buy a separate pair of waterproof shoes.
If you're just riding a mile or two you don't need expensive stuff, you can bike cheap stuff and bike at half speed. But 30-50 miles - you're not going to save money with it. You can bike in the rain at 30f-50f, but it's fairly expensive to do so.
I would also recommend making sure you have tires that grip well in the wet. Some are awful, some are pretty good, none are as good on the dry. Continental gp4000's do well in the wet. Whatever came with my specialized road bike a decade ago are terrible, lol.