How formal should a blog be?

When I started this blog, I wanted it to be an informal, chatty blog rather than a structured piece. I'm aware that people who make a living by blogging and vlogging have a method behind their blogs, whether it be planning them, scheduling posts, making timeplans and that's what I wish I could do, instead I write a list 5 minutes before saying "blog about college, blog about photos" and then I'm like "BLOG ABOUT WHAT?" I can ramble on for days talking about nothing of any use...like this! Anyway, I sometimes write posts and then delete them because I realise I just go on and on and on. If it hadn't have been for my PPD project at college I probably wouldn't have blogged again, but it has made me want to continue blogging, even if it is about useless stuff. So my question is: How formal should a blog be? Should it be a smooth running blog that links through the sentences and photos or should it be a more relaxed, spur of the moment sort of job? Personally, I prefer reading blog posts that are quite casual and chatty, with the odd joke thrown for a laugh.