Yeah, it's 12mm & 14mm for the axle adjuster nuts.10mm/12mm? Or is it 12mm/14mm?
Your best bet would be to buy a set of metric combination wrenches from Craftsman or Kobalt... both are decent quality for not a lot of money. Get a basic set that has 8mm to 17mm. Having a set of 3/8" drive metric sockets in the same size range will also come in handy. For wrenches & sockets larger than 17mm, it's more cost effective to buy those individually.
For the 19mm & 24mm sizes, I'd go with a socket in 1/2" drive. I recall you said that you've been working on cars, so I'm assuming you've got 1/2" drive ratchets. A 1/2" drive breaker bar would be good if you don't already have one.
Check out this sticky for a more comprehensive list of tools: http://www.cbr300forum.com/forum/how-forum/162-diy-motorcycle-service-maintenance-basic-tools-supplies.html