I was fortunate to get the Surface 4 for work and the normal configuration comes with the dock, Ethernet adapter and I opted for display port to VGA adapter because I have two monitors. The Microsoft display port to VGA I think retails around $40. The first accessory I bought off on my dime was off Amazon, the VTIN universal display port multi port adapter. It comes with VGA, HDMI and DVI-D. This is my go to tool! I don't travel often but heading to different venues, I don't know what connections are available, so have 1 device that connect to virtually anything is a necessity. AND... it was only about $20+ !!! Seriously, for half the price of what Microsoft offered, I picked up 3 x the versatility of the standard port adapter. Useful and affordable!
I do have an Arc mouse which I like, (previous purchase) but I'm liking the new Surface Arc mouse that is coming out. I've tried it out at a local demo. Almost same design, however it doesn't have that middle strip of buttons visible. This is important because I'm finding the buttons are getting stuck a bit with little flecks of dirt, etc., With the new Surface Arc mouse, it's all one body, so no more potential issues with buttons jamming. Again, it isn't out yet and for about $99, I don't think I'll rush out to get one right away, but if there's a sale and my current mouse dies, then yes, I will be picking one up.