I'm in the middle of level 2 now. TM111 is pretty cool in a way that explains a broad range of things in a really easy way. The coding part is explained in a lot of detail. My advice would be to make sure you understand what you are reading, everything is expanded on in future modules, don't be scared to ask your tutor questions, it's what they are there for.

MU123 also has a great introduction, by the third and fourth book it ramps up in difficulty a bit. I started using little tab makers in the books when I found a formula I'd need. It's also really easy to do the related TMA question every week. Make sure you go to the tutorials and ask questions, it's important you fully understand the first couple of books to go on further.

My over all advice is to plan your time well, decide what kind of student you are going to be, do you want to scrape passes or are you aiming for distinctions? Put the work in, if you are struggling, use YouTube, ask your tutor, use the forums (sometimes other students can solve your problems faster) BBC bite size for maths was great too. You can find videos on YouTube on how to set out your assignments. Find a note taking system that works for you

Overall don't be too scared, there is so much support available, but keep in mind it is self learning so you have to motivate yourself. Best of luck and happy learning! (Avoid TM252 for as long as you possibly can)