It's a very fine first result I think! I like how you have intermixed various colours in the same surface - this is just how an apple looks, remniscent of subsurface diffraction. It's a pretty advanced technique, not many first paints get that right.
For some feedback: You might consider going over the edge with an eraser to sharpen the edge (this further marks the hard, smooth surface). Furthermore, if you slightly smudge together the brush strokes of the the area
facing us (only), you will help enhance the 3D-feel a bit methinks. Just some minor ideas.
There is by the way nothing "cheating" about using a reference. Noone can keep the detailed structure of every object in memory at all times. Your goal is to create a compelling image, use whichever help you feel you need to reach that goal. Keep it up!
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Griatch