I would say front first. Thats what ive done. And the reason i say so, is that is not only your front suspension, but it also plays its part in your stearing. Sure the rear will help you land jumps and bumps, but the first thing to hit anything is going to be your front end. So if you have a crappy front suspen. then it will bounce your teeth out and send your bike into a bad setup for the rear suspension to try and make up for, which in most cases, it wont even have a chance!
Put Shee shocks up front and a 400ex rear shock, and you'll be golden, (cause i think your as strapped for cash on your blaster as I am!)