I agree with Tang Ho, but for a beginner who is trying to learn these quite basic characters it's not really a practical suggestion to advise them to learn more advanced characters at the same time.
Fishuman's answer also has good information but I think I can give some practical advice, from the viewpoint of someone who quite recently learnt these characters starting from scratch as an adult.
Here is my advice.
Learn 部，陪，倍 all together. Each of these is of the form X+咅, or 咅+阝for 部. Learn what the components X, 阝 "are" (more or less: town, mountain, standing man - there is some information in Fishuman's answer, and plenty elsewhere in references/textbooks. I recommend the Outlier dictionary, Mini edition, as an add-on to Pleco. Pleco (the paid version) is also a very handy tool as it gives you a list of all the characters derived from 咅, ordered by frequency of use).
Learn the associated Pinyin; notice the similarities and differences between the pronunciations. Find your own way(s) to remember this information, at the level you need. It can be useful to lean that 咅 is made up - visually at least, in modern Chinese - of 立/standing and 口/mouth, but not vital to remember this information initially. (For example for me, I started out by concentrating on reading, not writing. So I just needed to recognize the combination of the meaning component with the sound component 咅 which for a long time for me was just a sort of squiggle that I hadn't paid much attention to.)
Use the method advised by Tang Ho (associated terms) by learning associated terms as long as they are not too complicated for your level. For instance, learning 部分，部门，加倍 will be helpful initially. 部队, 部署 will also be helpful, but later on.
Further steps: learn 赔,剖 and 培 and other related characters, and related terms like 赔偿，剖析，部队，部署 as you encounter them in your studies.