Financial questions that need an answer

I’ve just registered as self-employed,(domestic cleaning) and am in the process of making my way through all the paperwork,insurance and in/outs involved.
What I’d like to have an answer to is this.
I’m only expecting to make a small amount a week to begin with and have been told that I should pay myself a wage,but how much do you pay yourself and leave enough in the business statement for supplies,insurance,taxes etc?Is there a calculation/ratio.Also is there a limt to how much you can take out as far as the tax man is concerned?Still need to find a spreadsheet to keep accounts.
On another note,I’m a sole trader but want to use a business name.I know I have to use my study with the business study but do I have to place the term “trading as” on business cards,invoices.Can I omit these words as it makes it sound a bit of a dodgy business.
I would love to hear from anyone who can help