I believe we should first investigate the beginnings of life on Earth (even slightly) because this will help us determine if there were indicators that life would develop here, and we can identify any comparable signs elsewhere in the universe that suggest life may soon appear.

In my opinion, the primary objective should be to conduct research on planets and life forms that are similar to our own. I believe that the chance of finding forms of life on those planets will be higher due to the similarity between ours and those. Additionally , being able to contact and interact with those forms of life (if ever found or even existing) would also be greater . However, there should be other research on different planets (like the gaseous ones) because we may find other types of life that are not similar to ours under various dissimilar circumstances.
Another point in that regard is the resources; logically, it would be better to spend those resources on the higher-chance planet for having life rather than on those where it hasn’t been proven that they could contain forms of life . Regardless , research on other types of planets not similar to Earth can also provide us with new information about the universe, etc.