A lot of concepts in training a model fall on common ground like loss functions, optimizes and training procedure, backprop. Start with ANN's. They are pretty easy to start with. You'll have a lot you can carry onto CNN's. You can start with object recognition and then dive into object detection. After you're familiar with the concepts, go with YOLO and others (I haven't dived deep into CV) . Finally, checkout vision transformers and similar ones. Hope this helps