your bike is wanted by stunters everywhere, that bike is perfect.
In first gear...cruise about 30-35 mph, pull that clutch in, rev it a bit more (just do little increments until you get to the point you need) and slip it back out. It sounds like you know how to clutch it up, but the trick is having enough revs. MAKE SURE YOU'RE ON THE THROTTLE AFTER YOU CLUTCH IT UP; and apply as neccesary to keep it up.
I can be going 55 mph in first, and clutch it up to balance point so your starting speed isnt really critical, but slower speeds are easier (not below 25 when you're starting out with wheelies tho)
all it takes is practice.