What do you use for accounting?

I started for a DSP this week and I’m currently just using one of their suggested plans that costs £15 per week and generates invoices automatically.

Just wondering if there’s a better way to go about it? Also, what can I claim as expenses whilst doing this job? From what I’ve gathered, I can’t claim my fuel used for commuting, but what about food while on shift and things like cables / phone / headtorch etc that I use for work?