I agree with @falconfeast, first learn to use the cardano-cli. This is my main interface with cardano and it gets you started.
I learned a lot from it and the overall structure of the cardano network. I do not know what you are trying to build so its is a bit hard to guide you in the right direction. What I first did was to build bash scripts that use the cardano-cli to automated interactions with the cardano blockchain (send alot of transactions, mint/burning of tokens, sending metadata transactions and interacting with smart contracts). One can do alot with the cardano-cli.
If you are here to build dApps you also need to learn plutus, I myself am doing just that. To get started with this first learn Haskell (after you get the cardano-cli). Then one can use this knowledge to view the plutus pioneer lectures. I learned alot from them and especially lecture 6 in which a whole dApp is demonstrated from first principles (its a long video tho). From there I learned how to setup a working environment to developed and test plutus scripts using the haskell package builder cabal (this is all explained in the pioneer videos). Right now I am building simple plutus scripts and deploying them to the testnet.
Lastly it is also advisable to learn about the overall abstract stucture of the cardano network. Who is doing what and what information is transmitted when, how is this information parsed my nodes etc… For this I read all of the formal specifications of IOHK (they are on their website). Its a big pill to swallow but definitely worth it (just ignore the math bits, the text provides a good story of the overall).
I personally think the documentation is great, but it is somewhat cumbersome to find the right info if you do not know where to start. The cardano foundation is working on that, they launced a great platform not so long ago, see the website https://developers.cardano.org/.
Good luck and if you have any questions, just ask We are all glad to help each other out!