I'll never play in the rain unless I have too, but the key is top rain gloves like Footjoy . In fact they grip better the wetter they get. Also if you wear glasses get contacts. I never wear my glasses for golf but if you are a player who does not mind playing in the rain and wears glasses, invest in contacts.
Also get a nice roomy CLEAR RAIR COVER for your bag. Not a tight one. Get a roomy one.
Gortex Rainsuit is also a great item. I have the Foot Joy one both top and bottoms and it keeps you dry. My friends are always asking to borrow this one when they go on a golf vacation.
Lots of towels to keep the seat on your cart dry so you don't get a wet butt.
And a good gustbuster umbrella.
I have all this junk and still won't play in the rain
brianf