Most small business owners will either choose £8,164 as a salary (free of tax an NI) or £11,500 (tax free)
If you are not eligible for the Employment Allowance, then £8,164 will probably be the best option, it will reduce your corporation tax bill by 19% x £8,164 = £1,551
If you can claim the employment allowance then £11,500 will probably be best because that will save 19% x £11,500 = £2,185
Less Employee NI to pay at 12% x (£11,500 – £8,164) = £400
Net Saving £1,785
Beyond this you will pay income tax at 20%.
So in summary, I think the optimum salary is £11,500 or £8,164
Above this you should take dividends. The Dividend Allowance for 2017/18 is £5,000.
This is a simplification and you should speak to your accountant about your specific tax affairs.