The best way for you to start modding is to start mapping as well as improve as a player. In order to mod effectively, you need to know how maps work, and that's best learned through experience.
The way modding actually works, though, is that you identify issues in a map, communicate them to the mapper, and suggest ways to fix them. The commonly accepted "optimal" way to write mod posts is to follow a problem-reason-solution structure: point out a problem, explain why it is one and/or why it exists, and suggest a solution to the problem. This format will help you write clear and actionable mods.
There can be lots of different kinds of issues in a map: trivial things like missing hitsounds or clear Ranking Criteria violations, too much or too little contrast between sections, excessive gaps between two difficulties of the set, individual unfitting rhythms or patterns, and so on.
However, most of the issues modders point out are either easy stuff that the mapper missed or forgot about, or spots where the map does something that doesn't align with what the map seems to be
trying to do as a whole. That's where the need for mapping knowledge really starts to show up: you have to be able to identify what the mapper wanted the map to be like, see that some element of the map doesn't support that goal, and find a way to make it fit.
Now, you
can still mod with limited or even nonexistent mapping knowledge; lots of people start modding before they're especially good at mapping, let alone masters of the craft. It often helps people get better at mapping by applying their knowledge in a different way. The extent of your mapping knowledge just acts as a sort of cap on how effectively you can mod maps.
In your specific case, assuming you have as little mapping experience as your profile suggests, you'll probably be able to find RC violations with
Mapset Verifier and point out stuff that doesn't feel good to play to you. However, the latter will be pretty heavily limited by your skill as a player, seeing how your top plays are below 3* in every mode.
Good luck, though.