I joined very recently (yesterday)

I’d suggest having a go at the challenges that have come out already (1A, 1B, 2A, 2B). Pen and paper can get you very far and is great for building intuition – if you’re feeling adventurous you could try writing a Python program to decrypt or break some of the existing ciphertexts. @Puzzling_Pelican recently published a guide to solving Caesar ciphers in Python which you may find helpful. This week’s challenge is often a substitution or block transposition cipher – so worth reading up on those.

To add to the post from @upsidedown, it is worth doing challenges 1A-2B to get a sense of the storyline, as names can be really useful for cribs at the start and end of letters. Good luck!

Seconding the advice above! Welcome aboard and I hope you’ve been enjoying the story and challenges so far! If you’d just like some general advice on how to approach ciphers rather than a ‘how to crack ciphers’ guide, I’ve written some stuff that Harry kindly put on the News page: https://www.cipherchallenge.org/crackerjacks-guide-to-getting-unstuck/

I hope you find something helpful there. Good luck and have fun!!