As has been mentioned before an exact amount of percentage is tricky, we should look at what the needs are and then work out how to pay for that. On that note, we should be ensuring that everybody who wants to has a roof over their head, heating, food, medical needs met and an education with a route into work as an absolute minimum. Other public service like transport and infrastructure should be considered next and then we should be thinking about funding the things that are vital for a functional society like culture and sport. When this has been added up we can work out where this money comes from.
I think most people just want a taxation system that is fair, so no section of society suffering less than anyone else, they want a system that does not have waste whether that is through fraud, dodgy contracts or just plain inefficiency.
My personal opinion is that we need to level the playing fields between the likes of low taking paying companies like Amazon and their local competitors, the personal tax system should be more granular down to individual percentage points rather than massive jumps like 20-40%. 50% is not a high enough level of tax for the richest of people, plenty of countries have a more punitive tax system and they do not suffer from these people leaving the country.
On a personal level I don't pay enough tax as I can see we don't meet the basic needs of everyone in this country. I cannot fix this alone, even if I gave all of my savings to charity, it needs collective effort and system change, closing tax loopholes, stopping fraud (see Covid PPE) and if necessary raise the income tax rates but we also need to look at how the revenue is spent like the £500 lightbulb examples in the NHS and paying for ministers to go on holiday.