You also need a monitor with HDMI input, or a very obscure--powered--slimport-to-vga box (it's clunky, and of a very specific design) if you must use vga. I tracked it down on German Amazon, not available for shipping in U.S.. The slimport to HDMI is the only real proven solution; There are countless forum posts around the web where people are trying to get slimport to vga and reaching dead ends. Buying a new monitor, if necessary, is the path of least resistance.
I'm just setting up convergence myself. I'm very impressed with my Motorola 89451N Bluetooth keyboard; got it cheap and refurbished on ebay, and it's super sturdy. My mouse however is a bust, I'm looking to see what's proven in that department, and you might want to follow along here: https://forums.ubports.com/topic/2318/known-working-bluetooth-mice-for-convergence
If anyone knows of a slimport usb-hub solution, that would also be an ideal accessory. I'm going to attempt to daisy-chain an OTG hub with micro usb power through the micro usb power connection on the slimport adapter, when it arrives in the mail. I'm not holding my breath.
As mentioned above, don't be fooled by MHL hdmi usb-hub combos, Nexus 5 is strictly slimport.