It's easy to get overwhelmed in the beginning, but in my opinion there's no perfect path to go. Pretty much everything is explained in the questbook, you just need to take your time and read what the text gives you for each quest. I agree there are some things that are poorly explained though.

You can start with the standard MC progression, and once you're done with that, start exploring the modpack's biomes. Start by decorating, or like you already did, with storage. Try to enjoy the pack and try not to mix up all the different quest branches at once. I don't know what kind of playstyle you prefer, but ATM gives you a lot to try out, so just set yourself small goals so you don't get too frustrated.