The amount of knowledge of the Torah is so large as to be infinite. Even if a person would live as long as the prophet Eliyahu, he would not manage to know even one thousandth part of that which can be known. It is well known that in heaven one is punished for that which one could have known but did not try to know, and on the day of judgment one will be asked about (why one has not learned) the Maaseh Hamerkavah (description of the chariot at the beginning of the book of Yechezkel) and all the secrets of the Torah. It is, however, true that Hashem does not come with tricks to His creations, and will not punish them for something which would have been impossible for them to do. It is totally dependent on what he was capable of learning. Nevertheless, one should start off by learning those topics which are more relevant to his day to day life, like the common laws or the study of ethics and fear of Hashem, and what is the best way to serve Him. After that one should make an effort every day to acquire a new piece of knowledge, which he had not previously known, and try and acquire completeness for his soul, and not waste the precious time, which he could have used to learn more.
