Alphabet
Probably the first thing you will want to learn if you want to learn Farsi, definitely do not avoid as it isn't as difficult as it seems and is necessary to develop a proper understanding of the language.
Farsi alphabet (the Arabic style alphabet also used in Dari):
Chai and Conversation Read / Write Course (YouTube video)
Easy Persian's Alphabet lessons (text based explanations)
Tajik alphabet (Cyrillic):
Omniglot (also has some resources for Tajik at the bottom)
Absolute Beginner Resources
These two websites can be good places to start out with phrases and basic grammar that slowly build up.
Easy Persian
Persian Language Online
Dictionaries
Dictionaries for Farsi are in general incomplete and you will likely need to use various sources to get an accurate idea of words.
New Persian-English Dictionary (Farsi to English; generally very helpful contains lots of entries even obscure words, however does have some mistakes here and there and does not contain modern words)
Wiktionary (Farsi to English; can be used especially in the beginning when just learning common words but it pretty barebones overall for Farsi)
Abadis (Farsi to Farsi, Farsi to English; probably the most comprehensive dictionary online, contains modern words and obscure old words and importantly has comments for entries so you can learn more for entries that don't have good explanations, however to get the most out of it you will need to know a certain amount of Farsi in the first place as the useful descriptions are in Farsi and the Farsi used for Farsi-Farsi dictionary entries is often overcomplicated)
Vajehyab (Farsi to Farsi, Farsi to English; almost entirely overshadowed by Abadis as entries are the same except they delete words that are rude and there isn't discussion)
Even using all of these dictionaries you will still be forced to ask native speakers lots of questions while learning because none of them are comprehensive enough.
Grammar
Would generally advise you to use textbooks here as they are more comprehensive.
Textbooks:
Basic Persian: A Grammar and Workbook (Routledge Grammar Workbooks)
Persian: A Comprehensive Grammar (Routledge Comprehensive Grammars)
Colloquial Persian by Abdi Rafiee
Persian in use: An Elementary Textbook of Language and Culture (Iranian Studies Series)
Websites:
Easy Persian
Jahanshiri
GLOSS and ODA (online assessments and exam style questions that also tests and teaches some vocabulary)
Podcasts
Most of these you can find on any podcasting app by searching the name or just by searching on Google and using whatever site you prefer.
Beginner:
Chai and Conversation
Intermediate:
Persian with Dallas
Advanced (native level):
Navcast (anthropology and history)
Ravaq (horror and crime)
String Cast (science)
B Plus and Channel B (general knowledge)
I'd recommend if you are intermediate to watch YouTube podcasts as well because they have images that can help with understanding:
Deep Podcast (the most popular one, he has good visual aids and lots of videos to watch and other channels too)
B Plus has a Youtube account too and his videos have subtitles however less visual aids than Deep Podcast
Youtube Channels
Learning channels:
The Farsi Pod (conversations on specific topics, spoken slowly and with subtitles)
Persian Learning (grammar lessons and slow readings of short stories)
Intermediate/Advanced (native content):
maryjane reports (true crime)
AriaKeoXer (popular gaming channel)
MBC PERSIA (talk show and some TV shows, has subtitles)
Chat Apps
Very good for finding Persian friends all over, you will reveive an overwhelming amount of messages from Iranians and Afghans trying to learn English.
Hellotalk (on iOS and Android)
Tandem (on iOS and Android)
Teachers/Tutors
For in person teachers it will entirely depend on where you live and you will have to do your own due diligence, you can find classes in some universities and if your area has a large Persian population you can find tutors on tutor sites that depend on your location, search google for your location + Persian tutors.
italki (online tutors)
Dehkohda (online classes and in person classes in Tehran)
Farsi Subtitled Content
This is very hard to find in large quantities in Farsi because it just isn't common to subtitle with native subtitles in Iran however you can find some.
The hearing impaired section of Filimo has quite a few subtitled films (labelled با زیرنویس مخصوص ناشنوایان) and some of the TV shows (not labelled) are subtitled too. However getting access is difficult, you will need an Iranian friend who already has access or some way to pay them to gain access and you will need a VPN that shows that you are in Iran when you are not, which you can find out about here.
The aforementioned B Plus and MBC PERSIA Youtube channels have subtitles.
You can use this website to search for Persian subtitles on other YouTube videos as well.
Books
Depending on where you live it can be hard to find books, especially cheap books. Generally you can find various books online in the form of pdfs by searching the names in to google + pdf download, this will only work for famous books though. I can verify that iranibooks.com is legitamite and I have bought books from them and they sent it to Europe, however it isn't cheap. If anyone has ordered from any others I can add them. You could also ask an Iranian friend to send them if you have one.
Maybe getting a Fidibook e-ink reader for Farsi ebooks.
There are various websites for buying ebooks in general such as fidibo, taaghche and ketabrah (all of these also have apps). Most of them only sell in toman so you will need a friend, however I have seen that taaghche had a US dollar option (which was heavily marked up).
If you are looking to read poetry you can use ganjoor or the apps of ARS NETWORK (Google Play and the App Store), the app titled دیوان اشعار فارسی contains all of the poets or you can download individual apps for each poet and it allows to to favourite poems, mark poems as seen and bookmark.
Book Recommendations:
This is hard because I can't speak to what interests everyone and I didn't start in a good place and really never read a graded reader. If anyone has any recommendations for beginner books or graded readers please say :)
There are the obvious recommendations such as Harry Potter, you can find versions online by searching هری پاتر plus pdf download, or the more specific title which you should be able to find. This is good because you can read along with the English.
There is the great translation of The Little Prince by Shamloo that you can find online too however beware that it uses quite idiomatic Farsi.
As far as further recommendations that are not translations and more early advanced stage, Zoya Pirzad has a simple style. Houshang Moradi Kermani is also often recommended as his books are simple retellings mostly of the his childhood, however his books can have a lot of Kermani slang that makes it difficult to understand.
I can add more to this post when I find more resources or they are recommended to me. I don't have much info on Dari or Tajik as I am yet to focus on them so if you do feel free to mention some and I will add them. Thanks :)