I have some experience reading research papers. However, in my view, there is no single answer to this question (apart from this answer I am giving you, i.e. "it depends"). The answer to your question depends on
your background knowledge/education
- If you don't know much about the specific topic in the paper, you may need to study at least briefly the prerequisites for reading the paper, otherwise, you won't understand much about the paper.
why you are reading the paper
Are you just interested in or curious about the topic in the paper? Then maybe you can only quickly read it, or only read specific sections, such as the ones that introduce the technique (abstract, introduction, and maybe conclusion) and skip all the math; the figures are sometimes also insightful.
Are you doing (serious) research on a related topic? If yes, you will probably need to read the paper multiple times (at least the sections that you don't fully understand). It may also be useful to look at implementations of the approach. If they don't exist, you may consider implementing the approach yourself.
Do you need to present the paper? In this case, you may also need to read the paper multiple times, understand well the figures (because you will probably use them in your slides: an image is worth 1000 words, etc.)
how much time you have to read the paper
Note that these guidelines should also be applicable to other cases (i.e. when you're reading other types of research papers that involve math).
You may also be interested in the paper How to Read a Paper (by Keshav). It provides a few tips that could be useful.