It's taken me years to learn this, but always start with small, easy projects when using a new machine. It helps you learn the feel of it, the stride and speed you're most comfortable with it at. When setting up a new machine, I always start by making a big ole pillow. One of those long body pillows, usually in a substantial and easy fabric. Then I make some small pattern weights. The pillow is big enough that I can discover any "ghost in the machine quirks" and the pattern weights help me get the feel of curving with the machine. EVERY machine takes a curve differently, and there's not a lot of fiddling that can make it easier if your machine doesn't curve well. Some are good about curves, some you just have to force through full speed ahead.
I think making a plushie, if it's not too small or detailed, would be good starter fodder for learning the kick to your sewing machine.