Having the same grinder, and just having gone through a steep learning curve myself, my recommendations would be the following:
1) Ensure you keep the machine clean. Get some cafetto and backflush regularly.
2) Get a tamper that fits well.
3) Start by timing your shots, and trying to get roughly 60mL in 30 seconds for a double, or 30mL in 30 seconds for a single. Despite this not being an exact, its a good starting point, and timing/measuring made me realise I wasnt tamping hard enough, or grinding fine enough. The coffee improved, and I no longer measure/time. Look at the crema...sniff it, taste it, admire it, lust for it :)
4) (And this probably should be number 1) - FRESH BEANS - Personally I have found the consistency of single origins makes it easier to learn with, however this is personal preference.
Also, always remember that there is no such thing as perfect coffee for everyone. People can disagree on flavour, so now you are making it yourself, you can tweak it to what your tastebuds like. Dont ever let anyone tell you the coffee is bad if its what you like.