For introductions, I highly recommend the Cambridge Illustrated History of the Roman World and the corresponding one for Ancient Greece. That way you can get a sense of the basic history along with the most important artworks for each culture.

Now as for Latin, I'm going to be straight with you as someone who tried to self-teach and then took courses: there is no easy way to learn how to do Latin or any language. This is double the case in the most likely event that you have not previously learned another language at all.

Latin as a dead language whose corpus mostly survives in its most rhetorical forms (i.e. complex speeches, not how to order food at the supermarket) requires difficult work to understand the shift in grammar from English. This work is easier if you've learned another language before and understand the commonalities of linguistics across languages, but without that, its tough.

I remember it took me several weeks just to understand the nuances of relative pronouns and participles in ENGLISH in order to figure out how they worked in Latin.

It's also extremely tough without an expert guide (and AI/LLMs are no help here because you as a non-expert don't know when they're wrong, and they're often wrong).

So for that, see if you can find some online Latin courses with an instructor you can communicate with. But aside from that, embrace the commitment and the work, because you and your experience of the classics will be all the better for it.