I mostly recruit high WE players (75+), and I've seen some randomness between high WE players, but I usually see between 12-22 for players between their first and second seasons.
Small sample size here, but the most interesting thing to me is the lack of correlation between potential and offseason development. Here's a player that had multiple blues and greens left:
And here's a player with slightly lower WE with green PER and a few ratings that were black and the rest being yellow or red.