I am a college student who last studied History when I was in 10th grade. I don't know much about History and whenever I read about History in news articles, social media posts (some of them by Historians), etc, I always...like always, find contradictory things.
I live in India and whenever I try to read about the History of India I get extremely contradictory pictures: some say Gandhi was responsible for freedom of India, some say Bose was. Some say RSS (a Hindu nationalist party in India) was instrumental in the freedom struggle, some say they weren't. Some say Mughal rule in India was one of peace, some say Mughal rule was brutal against non-Muslims. Some say Aryan migration theory is correct, some say Aryan migration theory is false. Anything regarding ancient India, its religions and philosphies is basically a mystery. No one seems to know who wrote what, when and where. Some say Ramayana and Mahabharata were true, some say its not. When I try to find something about History of Kashmir, things are more complicated. I feel really lost and have no idea of what sources to consider legit and credible and what not. Any guide to tell me how, what and where should I lead about real and legit History?
It doesn't only have to be about India btw. It can be about anything related to History. I just want to know what should a non-Historian, a commoner, read to learn legit History.
A basic rule is to stick to material published by a reputable source. That eliminates 95% of anything published on the internet. If you pick up a book on the History of India, find out who published it and why. With the caveat that I know virtually nothing about the system of higher education in India: in the US or Europe, any book or journal published by a major University will be solid and will be very thoroughly vetted by blind peer review in the field.
A good place to search is a major university's library page. I have just visited University of Delhi's library page and find it a bit confusing to use, but that's ok! You can search on any library system, then when you find what you are looking for, you can then go see if a local institution has that same book. For instance, searching for "History of India" on Berkeley's excellent system will return 500 results. Or Oxford's excellent search tool. Or Yale. or Stanford.
As a matter of example: I find this book. Routledge (London) is a top-notch publisher. I even recognize that distinctive blue cover design, which many of their books have. This will be a quality contribution to the study of the history of India, and I know this based purely on the reputation of the publisher. It is from 2010, which is fairly recent. You can use this book as a starting point, because, being a quality publication, it will contain a full bibliography of sources. For instance, you can check out chapters 7 and 8, look closely at the footnotes and citations, and from there jump off to perhaps a dozen other books on more focused aspects of Indian history. Because it was cited from this book, you can mostly assume these citations will also be quality books themselves. And so on.
I think you've ran into a problem inherent in History and the studying of it, and that is that there is often no definitive answer to a question. This is doubly so the further back we go, or if contemporary evidence is scarce. The famous example is the Roman Empire. Despite literal millennia of discourse involving a wealth of information, European Historians can still arrive at entirely different conclusions from the same evidence on what caused it to collapse.
But, to answer your question, you need to follow the evidence. You have the example of the historian posting on social media. Did they give evidence for their claims beyond simply stating, "I am a Historian, listen to me?" If they supplied evidence, where did it come from? The closer to the time period and people involved in question, the better. For example, if they posted a contemporary scholar's account of Chandragupta's unification, then this is quite strong evidence. If it was an 18th Century British historian writing the same, it is much less reliable.
Material objects are also potentially strong evidence. If we study ruins and find Islamic artifacts solely in the poorer, less comfortable homes, we can infer that Muslims were less wealthy than others. We would then look for contemporary sources as to why. Perhaps a stone tablet from the era gave a proclamation against their faith. Perhaps there is evidence they had only recently migrated. Perhaps there is no evidence at all that explains why they had the lesser homes, in which case we can only infer that they were poorer.
The above scenarios are all examples and not factual in any way, but stand as an explanation of the process. Get as close to the time as we can, in writing or artifacts, and see where it leads us. For the average person, some healthy skepticism and willingness to chase claims down to their sources are key. Any good historian will at least suggest reading material to back their claims, if not physical evidence as well.
When you're looking for sources in books and online, it's important to keep a few things in mind. First, look at where your source comes from. If it's an online source, is it a reputable site? What kind of biases may the authors have and how does it affect the validity of the source? You will also want to look at the year it was published. How has the thinking on this topic changed? The best kind of source to consider is peer reviewed articles in journals. The journal's board basically does the hard work for you-they deemed it has scholastic merit! You might encounter a pay wall with some journals, but Google Scholar and the databases in your local university (if you're a student) or library can get around those.
Another thing to consider is primary vs. secondary sources. A primary source provides first hand evidence about a subject. Secondary sources describe, interpret, and analyze primary sources. For example, newspaper articles can be both primary and secondary sources!
As other commenters have pointed out, sometimes the scholarship doesn't offer us a definitive answer. Once you can distinguish what a good historical source is, you'll be able to draw your own conclusions based on what you've read.