Well, I can offer a definite "that depends." It depends on your height, your inseam, how you intend to ride, where you're located (mild weather or serious winters and summers), whether you have broad or narrow sholders, and a number of other things. Like Texas Governor Rick Perry, I can't remember them at the moment!
For me, the the stock windshield doesn't offer enough protection so I changed it - at the moment it's the MRA Vario Touring with the adjustable upper section. It's not perfect but it's good and doesn't look like socks on a rooster.
I have (apparently) broad sholders and didn't particularly like looking at them in the mirrors so I changed them - to KTM 990 Super Duke mirrors and like them a lot mostly because I can now see what's behind me.
I also added Moto Werk (Speedy's) foot peg lowering blocks because it makes the riding position more comfortable for me. I would get thigh cramps now and then which made for some curious riding positions.
I tend to want to carry stuff (rain suit, tool kit, mini pump and patch kit, the kitchen sink) so I added Givi hard cases and also like them a lot - they look good (in my opinion) and are durable.
My backside also appreciates the Corbin saddle that was on the bike when I bought it. Some like the Corbin while some don't - sort of like most things in life. For me it's worth it.
I also replaced the stock horm with a PIAA which mounted in the same location as the stock horn and is, thankfully, much louder. Vehicles can actually hear it, and that's a good thing.
Virtually all my riding is on paved roads so I haven't added hand guards (Barkbusters seem to be favorites among members of this forum), or engine guards (yet). Though I haven't tossed a motorcycle since June 1972, engine guards are the next addition I'm considering. And with my luck, I'll probably toss the Versys a day after I install the engine guards!
Before all of these possibilities, however, should come the riding gear that will protect you, the most important part of the equation. The other stuff is, quite honestly, incidental.
Certainly others will offer advice that is as good or better as most of them have had their Versys longer than I've had mine. Still, it's a great machine to spend money on personalizing (whatever the currency may be). Enjoy the ride.