So I'd like to learn Spanish. I'm in the US so Latin American Spanish would be the best choice for me. However, there are two resources I really like (Assimil and StoryLearning) that use Castillan Spanish. Would it be advisable to completely avoid any resources for that dialect?

I feel like I have to avoid anything other than the kind of Spanish spoken here, but I'm not sure if that's the best strategy. I know the basic differences between the two, but I'm not sure how to really start learning now or even what to do when I'm able to understand more. I don't even know how big the differences in books are. Is there a different past tense in literature?

I speak German around a C1 level so I'm used to learning a language. I'm just kinda confused with Spanish.

Should I always make sure it's a Latin American Spanish book or is that overkill? If you learned Spanish as a foreign language, what did you do? Did you completely avoid other dialects and resources you'd otherwise enjoy?

Thanks for the help.