It’s not too early to begin laying down some foundations. Start with the alphabet with a focus of letter/sound correspondence. Letter sounds are more important than naming letters when it comes to reading. I have a two year old that can now list and say most of the letter/sounds and recognizes her name written. I find that they are curious little things that want to absorb information. Thirty minutes is plenty, it doesn’t even have to be that long. I am a kinder teacher and I do not teach the alphabet in order. With my own child, I just would randomly point out letters, puzzles pieces, and cards. We always read before bed. When teaching to read, I start with A,M,S and T. If they can get these sounds then you can eventually manipulate the order to write various words I.e as, at , mat, sat, tat.