We have a Getting Started section on our wiki.
For machine learning, I can really recommend Andrew Ng's introduction course, and then maybe deeplearning.ai (although I haven't tried it). Also, here are a bunch of free books. I recommend Elements of Statistical Learning, but from the titles it seems a few others may be more introductory.
For things like image recognition, object detection and computer vision in general, you may want to check out /r/computervision. I haven't personally tried these, but there are also courses on Udacity and Coursera. There's also this book of which you can freely download the draft version.