150 grams is still very small and very young (keep in mind they grow at a different rate), since you have limited experience I would recommend something that is in the 100 grams range, this means a very well started animal. If you get one that is in the hatching weight range and your husbandry is not optimum right away the animal can go down the hill very fast, I have seen it over and over year after year.
Based on that I actually don't even let go of my animals anymore until they reach 100 grams (unless they are sold to experienced keepers)