It depends what you are painting! If you’re looking at smaller models/tabletop minis, you should take a look at setups used in the minipainting communities. Larger models might benefit from different setups. I know I didn’t want to start cheap and have to upgrade later, so I jumped straight for the Iwata HP CS. The dual action is super nice to have (not a must have though). I’d also recommend spending more on a better compressor before a brush (I got a simple 1gal compressor from California Air Tools).
I’ve had a lot of success taking the rules that YNAB uses and applying to my own budgeting method. I recommend checking out Actual Budget if you’re capable of self-hosting and want a fancier software instead of a spreadsheet. The rules are key, though; pick a methodology/mindset you agree with and stick with it.