It's never too early. The concept of readiness is a myth that has been perpetuated by nappy companies. 100 years ago kids learned to use the toilet between 1 to 1.5 years and now it's 3 years. Kids in developing countries that don't have disposable nappies are using the toilet around 18 months. They're no different to children in developed countries. Start by introducing it, after a nap, before bath etc that kind of thing and just go from there. You can try nappy free and try catch the wee/poo. It's a process anyway.
If he's one that likes to follow you to the toilet I'd pop him on the potty when you go to the toilet as kids obviously love copying mumma and I'd also pop him on when you do nappy changes. If you happen to catch him doing something in the potty make sure you make a huge fuss and praise
It’s pretty early for active toilet training. We had one from around that age and my little boy would play with it, so the occasional wee on it. Get one and put it in the bathroom and he can get used to sitting on it from time to time so it’s not new/scary when toilet training starts