Welcome to the forum!!
Gas mileage and oil consumption will suffer a little until the engine gets broken in. This can take up to 2000 miles before you notice everything stabilizing. Keep close watch on the oil just as you are doing. You should not wait until the 600 mile check to change the oil. Do it early and often throughout your break in period. You will extend the life of your bike tremendously if you do. For instance: Oil change at 50 miles, 200, 500, 1000, 1500, 2000. Since it only holds a little over a quart and oil is cheap, this is a great way to get a lot of mileage out of your bike. Your bike will love you for it. And again, Welcome!!