Start with Let's build GPT: from scratch, in code, spelled out. (116 min, Andrej Karpathy), then Transformers, the tech behind LLMs (27 min, 3Blue1Brown). All 203 lessons here are free, from the teachers' own official uploads. You'll need gpu-ready laptop, laptop stand, noise-cancelling headphones (about $1310 of kit). The book to keep beside you: Deep Learning with Python by Francois Chollet.