Water getting on you from above is one thing. This can't be avoided. Water hitting you from the ground that's got dirt, grime, oil, and whatever else, can be mostly avoided with a good set of fenders, preferably long mudguards.

Shoe covers are necessary too if it's a heavy rain or lots of standing water. There will be spray from the wheels that will get on your shoes, regardless of fenders.

You'll get wet everywhere else. Just makes sure you have good moisture wicking baselayer to take the water away from your skin.

A good jacket to keep your core from getting too soaked.

That's about it.