Often when you're worldbuilding, you get tired of making shit up all the time. Or you are worried about the details of a particular situation and its ripple effect. You have a couple options for learning from world history.
There's three general situations you could be in:

1. you're modelling your fictional culture (FC) heavily on one real culture (RC)
2. you're modelling your FC as a hybrid of different RCs
3. you are NOT modelling the FC on any one RC, but have a culture-related question you need to answer or specific element you want to adopt

Starting tips:

-understand WHY people do things. social systems and beliefs don't form out of nowhere. They either are done for some practical purpose or they reinforce pre existing systems. When they don't work, they adapt or disappear. This can include everything from the economy, to religious organizations, to beauty standards. A key part of learning about cultural practices is getting down to this logic, because even if it looks strange, there is an explanation. Also, the more you learn about a culture, the more context you will gain for these decisions.

-learning from natives. Going in hand with my last point, things only look strange from the outside. The best way to overcome the sense of exotic allure a lot of outsider sources will instill is hearing it from the people actually from this culture (or dedicated academics & descendants of a historical culture). They understand the basis of these thoughts without perceiving them as strange in comparison to something else. For a modern culture, getting a firsthand view from a native person (via books or youtube) or broadcasting channel in the country. For historic cultures, finding first-hand sources, such as diary entries, art, or recordings when available in your language would be the best equivalent.

-be conscious of stereotypes. If you're able to find a piece from a native about their liked and disliked depictions in media, then listen to it. interact with other media that depicts the same culture, and familiarize yourself with archetypes that these stories fall into, or the characters from the culture. seek to avoid them (you don't need to intentionally subvert them and/or give obtuse amts of attention to how you're NOT FOLLOWING STEREOTYPES!1 because at the end of the day you're still recognizing them)

-gain a background. this is the most obvious one. This is not just the surface elements of culture like dances or clothes, but the greater history and schools of thought in this place. Understanding what other cultures it has/had major interaction with and its primary ideologies is a piece of this. Encyclopedias are great for getting familiar with the general course of history of this culture, especially if it's one you aren't already that familar with.

i. basing heavily off of one real-life culture

Choose your parameters: both the ethnic group and time period. It can come off as miseducated to group large swaths of similar cultures in together as if they have no real differences. For example, instead of "Vaguely Middle-Eastern", choose "Lebanese" or "Palestinian". Time period could be a bit more flexible, and unless you are writing hisfic you don't need to be THAT exact. Learn about the eras this culture has gone through, its depressions and golden ages. Pick a period to focus on, as cultures in the real world change with time and so should yours. Specifying (even if never explicitly said in-world) makes your job of researching easier and makes the culture more unique compared to what's commonly found in fantasy. I'm sure people who are from these cultures would be refreshed to see an author do their research and put appreciation into their history.

Avoid Cross-Mixing: Learning about a specific culture means you're probably gonna run into its neighboring cultures, the ones it bears the most similarity to. For example, to an outside eye, Chinese and Japanese cultures might be hard to tell apart. This isn't inaccurate entirely, as China has influenced Japan for over a thousand years. However, learn the differences in order to not conflate them: there are some things that never took ahold in Japan, and for the things that did, for example green tea, they have been adapted into uniquely Japanese things, like the matcha tea ceremony. Likewise, Japan has had its own ideologies, intellectuals, and practices that were not brought from elsewhere. Looking for things unique to your RC means that you can avoid unintentionally using symbols that belong to another one (or, at the least, are most commonly attributed. The chinese zodiac is not *nonexistent* in Japan, but it is much more strongly associated with China). To specify, by 'cross-mixing' I mean confusing symbols between neighboring cultures and not deliberate hybridization.

ii. making a hybrid

Compare and contrast: understand these cultures and their differences well enough to contrast them should they mix. Where do they already meet and how are they different? For example, mixing the Maori warrior culture with the Samurai caste of Edo-era Japan. Obviously these are both warrior cultures, but how else do they diverge? Each has unique practices, haka and seppuku, which play different roles. Why do they do these things? If there are conflicting beliefs or practice, which do you like more? You can always just make things up to be a glue.

Decreasing the natural difference between these cultures might save you some time. Maybe choose cultures that already have a base element in common: for example, maritime cultures. Even if these two RCs never interacted, they probably would have run into the same logistical problems and have developed similar practices. For example, two entirely different maritime cultures would develop complex ways to navigate the oceans, how to store food for travel, as well as how to pass the time when stuck on a boat for several months. Even beliefs like sea gods and monsters could start looking similar.

Still, avoid cross-mixing. Read what I said in part 1, with the addendum that if you are hybridizing similar enough cultures, you can again run into the problem of seeming uneducated about either. Real-life hybridization has already happened between them as an effect of cultural exchange. You can also create new motifs based in a combination of these real world practices, which look unmistakeably unique. One of my favorite movies, Tekkonkinkreet, features a city with a beautiful, unique pan-Asian aesthetic. I think the line here is in looking like you have intentionally created a new cultural aesthetic (which you have creative license to do) versus just not knowing the difference.

iii. you have a specific question

Research! Yeah, obviously. A single similarity wouldn't imply any deeper link between your FC and any RC you might've borrowed from, if you find yourself in a particular situation. For example, you have a group of civilizations on a continent where they have no large, domesticated animals (such as horses, elephants or oxen) to do draft labor. Instead they may adapt either by using smaller animals (such as dogs), doing that labor differently, or just avoiding that type of labor. A real-world equivalent would be found in the Americas, before Europeans arrived. Dozens of cultures found ways to do the work they needed without large draft animals. Taking this for a fictional culture wouldn't imply that they are fantasy native americans, just that they have the same combination of factors going into their practices. (Of course, if there are even more similar factors, you may lean into that a bit more).