In looking at the PDs for some ideas, I took a clue from Cyril Bailey's summary of the PDs. He categorized them as:
1-4: The tetrapharmakos, the four-fold fundamental principles necessary for a tranquil life
5: The relation of pleasure to virtue
6, 7: Protection from external disturbances
8-10: The selection of pleasures
11-13: The ethical value of physical science
14-21: The wise man’s life in relation to nature, his fellow men, and to true pleasure (can be sub-divided)
22-26: The tests and standards of moral (i.e., truly pleasant) action
27, 28: Friendship
29, 30: The classification of desires
31-38: Justice and injustice
39, 40: The wise man’s life in the Epicurean community
Now there are many things about which I don't agree with Bailey, but this list is helpful as a starting point.
PD01 and PD02 are the ubiquitous correct understanding of the gods and death.
PD05 gives the standard formula about living pleasurably entails living virtuously/ethically, and vice versa.
PD08 to PD10 talks about making the correct choices and rejections, the core of Epicurean day to day (moment to moment) practice. The practice seems to me to be brought up again in PD20 through PD26. Those are sections I need to investigate in my unending quest to re-compose Principle Doctrines as a text. PD29 (necessary, unnecessary desires, etc.) and PD30 are an important "how to do it" text as well.
PD11 to PD13 talk about the necessity of understanding "how things work" when it comes to allaying fears and superstitions about "astronomical phenomena and death and suffering," "myths," and "what is above and below the earth and in general about the infinite unknown." This conveys the importance of studying natural science and to understand how the physical, material universe works.
PD14 and PD15 talks about the fact that unlimited wealth isn't necessary to pursue a pleasurable life. Sufficient wealth is "limited and easy to acquire."
PD17 is a good reminder: "One who acts aright (δίκαιος) is utterly steady and serene (ἀταρακτότατος), whereas one who goes astray is full of trouble and confusion."
PD27 is our friendship one!
The Justice PDs are important from an ethical standpoint in that they say how people should treat each other, especially PD31 "Natural justice is a covenant for mutual benefit, to not harm one another or be harmed."
PD39 and 40 are not straightforward when trying to translate, but are potentially helpful.