Congrats on the new airbrush!! I had a 155 and it did a good job. For thinning the other guys gave you some good points.
If you plan on using acrylics MM Acryl is good to start with used with Tamiya Acrylic thinner. Basically twice as much paint as thinner is a good place to start with no matter how you measure it. You can adjust your ratio from there till you feel comfortable with it.
Also when you spray acrylics it's good to put a nice thin coat down first, let it dry about 5 min then shoot your other coats on top.. and make sure you clean your model with soap and water or wipe it down with alcohol before you paint, acrylics aren't tolerant of oils.
If you decide to stay with acrylics there's more you'll learn along the way. They're not near as difficult to use as some say, but if you always do a few things when spraying you'll get a great finish with little hassle...