As far as I am concerned, you're on a bike, you're not in an enclosed, sealed space so you're going to get wet. However, wet can also mean cold so I say yes to raingear (jacket only when it is mild or warmer). I agree with another poster that wet shoes are a real annoyance so shoe covers are nice too (to prevent, or at least reduce, rain from running down my leg into the opening of my shoe covers, I wrap a reflective leg band around the top of the bootie to tighten it up against my leg which will help but in torrential rain, may not be sufficient).

Another consideration is that rain reduces visibility so I would not invest in a dark rain shell but a brightly coloured one with lots of reflectivity.

Finally, I don't like rain running down my head into my eyes or down my neck into my jacket and down my back so I wear a helmet cover.

Finally, on rainy days, I pack a second set of gloves, socks, shorts and jersey so I can put on a dry set for the ride home.