I know this question sounds complicated and general, indeed.
I'm looking for some effective tips for people with this condition.
Language Learning Stack Exchange is a question and answer site for students, teachers, polyglots, and anyone interested in the techniques of second-language acquisition. It only takes a minute to sign up.Sign up to join this community
You can learn from all kinds of audio learning materials, basically. If you want to achieve high proficiency level in the language you will need to have a conversation partner at some point, but it is possible to reach a pretty decent comprehension level before that.
As for my experience: my first Mandarin audio course was FSI Chinese; I went through first 6 modules (which took me at least 100 hours of learning, if not more) before I started having any private tutors and conversation partners. And at that point my speaking comprehension was already quite good.
Among the resources I can recommend (and which are available for many languages) there are FSI courses, Praxis language podcasts (I used ChinesePod) and FluentU. Assimil courses are quite good, too. These are just examples, just look for anything that contains a lot of audio for your language and is suitable for your level. Most importantly, pay attention to the length of the materials in the target language - the more hours of audio the better. When you compare their lengths, take into account that some courses, e.g. FSI and Pimsleur, have a lot of English in their audio, while e.g. Assimil courses have only target language audio. Last, but not least, make sure that whatever you choose, it is something that you enjoy listening. This will help you stay motivated.
Note that some audio courses are very explicit in their methodology (e.g. FSI), while some other materials may be usable in many different ways (e.g. FluentU). If you don't have much experience with language learning, an explicit course may be better as it provides some framework. But in the end, it is you to make the decision what suits your purpose best.
As in many other cases, answer is "it depends" (on what L1 and L2 are).
If your L1 language is "hot" and of interest to learn by other people (in other countries), you can find online a partner for language exchange (tandem learning), who speaks your target L2 language and wants to learn your L1.
Real problem is if your L1 language is too obscure to be of much interest by speaker of your L2 language, so finding a tandem partner is hard.
In example: For a speaker of English, is much easier to find a tandem partner speaking Thai, than for a speaker of say Albanian. because many more Thai people are interested to learn English than Albanian. So for such Albanian aiming to learn Thai, an effective strategy could be to get to a reasonable level of a language desired by L2 speakers, like Italian, English, German, or possibly Esperanto (high enough to satisfy tandem partners).