I'm afraid to say that most people seem to find learning to shuffle
Very frustrating... it's just not an easy thing to learn.
Your equipment sounds fine to me but if you're after more information about what's good for 2D stuff then the
kit sticky at the top of the forum has a great discussion of just this. One important tip i had at first was that a slightly shorter string than you'd usually use is helpful; i used one that reached from the ground to just above my belly button at first.
The difficulty might also be to do with how you're starting the shuffle. If you've been trying with a throw start then i'd suggest trying a wrap, some people just find one more natural.
There's a huge amount of info in the thread
Starting and correcting 2 diabolos which might help you and i've also learned a lot from
barnesy's site. You must remember though that the key is probably going to be patience, you'll find you get smoother and can hold the shuffle for longer with the diabolos spinning faster and more evenly and then you can really start correcting and pulling tricks. When you get it, it feels great!
(then you'll find yourself in the position where i am now, where the shuffle seems easy enough but the tricks mostly evade you

)