Learning Latin on your own can be daunting, but it is entirely possible to build your skills in the language without a formal class or teacher. The key principle to keep in mind is called comprehensible input:
Comprehensible Input is the big buzzword in language learning at the moment. The fundamental shift in the way we understand language learning is that input, not memorization of grammar rules and vocabulary, is far and away the most important factor in language acquisition.
Input is any material in the target language (the language you want to learn) that you listen to or read. That input should be comprehensible, meaning you can understand it freely without stopping to decode it. The ideal is to find texts (spoken or written) where you already know the meaning of 90-95% of the words; you can often figure out the other 5-10% from context, and as you encounter more and more words your vocabulary naturally expands.
This describes an ideal language-learning environment. Our own situation will almost always fall short of that ideal for several reasons, especially when we're talking about an ancient language like Latin:
All the native speakers are dead. This means you won't be able to travel to ancient Rome, talk to friendly people, and build your skill in the language through conversation.
It is hard to find enough beginner-friendly Latin texts. Most textbooks assume that their audience is in a traditional classroom environment with a teacher who can compel them to study vocabulary lists and do grammar exercises. This means that the early chapters of a textbook will be fairly easy, but the difficulty of the texts ramps up faster than even a smart student's natural rate of language acquisition.
It takes a lot of input to build up to the level where you can fully engage with authentic Latin texts. There is a huge body of Latin texts out there, but even the easiest of these require a high-intermediate level of achievement in the language.
Learning Latin on your own will require a little bit of gumption, but if you're the kind of person who seriously considers learning a language on their own, it's something you can do. Here is a list of resources to help get you started:
If you want to learn Latin on your own, you need some texts to read. It's a good idea to cycle through textbooks, reading the Latin stories from each until you hit a "wall," then switching to a different textbook. By the time you've done this with a few books, you'll likely have less trouble with the part of the first book that was giving you trouble.
Textbooks Available For Free:
Cambridge Latin Course: Cambridge makes the previous edition of their Latin curriculum available online for free (Book I, Book II, Book III, Book IV, Book V). This is probably the most user-friendly textbook resource out there, and a good place to start when teaching yourself.
Operation Lapis: An online Latin textbook by the Pericles Group. The materials are all available for free here, but you can pay to track your progress and have access to the "gameified" elements.
Latin by Natural Method: A textbook from 1957 that is in the public domain and available for free here. The focus is more on Ecclesiastical (Church) Latin and many of the stories are drawn from the Bible, so some students will find the material more compelling than others.
Latin for Today: Another public domain textbook, this one from 1927. Find it here.
Textbooks That Cost Money:
Lingua Latina Per Se Illustrata, Hans Orberg: This is the most popular Latin text for self-teachers, and for good reason. The entire textbook is written in Latin, so you can spend as much time as possible thinking in Latin. It provides more input than any other Latin textbook, although it adds new vocabulary and grammar features too quickly to be entirely effortless for a beginner. It's best to combine "LLPSI" (as it is often abbreviated) with one or more additional textbooks to get the full benefit.
Via Latina: De Lingua et Vita Romanurm, Maria Luisa Aguilar & Jorge Tarrega: Another textbook in the tradition of LLPSI, Via Latina is shorter and a little denser than LLPSI, but it has better graphic design and more varied practice activities.
Once you've spent some time with beginner-level texts, you may want to start reading "real Latin." Here are some suggestions to get started.
Tiered Texts: A tiered text takes a real Latin text and provides simpler versions of that text as "stepping stones" to get you to a place where you can comprehend the unadapted version. You can try the tiered version of Julius Caesar's commentary on the conquest of Gaul here.
Easy Real Latin: These are the works that are the easiest for intermediate students to read:
Jerome’s Vulgate: a translation of the Bible into Latin, Jerome’s version was the most important book in Western Europe for over a thousand years. (Perseus)
Hyginus’ Fabulae: short summaries of Greek myths. Hyginus’ sentences are pretty simple and his stories are fun, if lacking in detail. (nodictionaries)
Eutropius’ Breviarum Historiae Romanae is a summary of Roman history from its founding up to the 360s CE. Like Hyginus, Eutropius tells these stories without much detail. (nodictionaries)
Nepos’ De Virīs Illustrīs: a step up in challenge from the previously mentioned authors. Nepos writes biographies of important people from Greek and Roman history. His Life of Hannibal is particularly popular. (nodictionaries)
Dictionaries:
https://www.latindictionary.io/: a nice, beginner-friendly Latin dictionary with a few other fun widgets including a Latin version of Wordle.
https://philolog.us/: an online version of the Greek and Latin dictionaries most often used in universities. Pick "Lewis and Short" in the top left to access the Latin dictionary. The information will probably be overwhelming for a beginner, but if you find yourself confused by how a word is being used, this will give many contextual translations and references.
Youtube Channels:
LatinTutorial: Straightforward explanations of concepts in Latin grammar.
ScorpioMartianus: A variety of Latin-related content, including beginner-friendly videos to accompany LLPSI and some modern songs translated and performed in Latin.
Found in Antiquity: Beginner-friendly Latin content, including some lessons taught through Minecraft
Magister Craft: A Latin teacher who has been recreating Rome from the time of Augustus with his students. Includes stories and lessons in Latin at a variety of levels.