Farage confirmed that the party's previous commitment to abolish national insurance and have a flat 31% tax rate was being "rethought" - but said he believed the top band should fall from 45% to 40%.
He also insisted no-one on the minimum wage should have to pay tax.
The comments came in an interview on the BBC's Andrew Marr show after Ukip achieved major gains in local and European elections.
Farage said his party was now "building up a really good representation" on councils in target constituencies for the general election.
He predicted they would focus resources on "two dozen, three dozen" seats next year, and win a "clutch" of them.
Farage has already disowned the Ukip manifesto from the last general election, and said he would set out a new platform at its annual conference in Ed Miliband's Doncaster constituency in September.
He denied it would be "Thatcherite", saying the Tory doyenne's approach belonged to another era.
Deploying the "cost of living" catchphrase used by the Labour leader, Farage said: "I want us to give millions of ordinary families and people in this country the opportunity to live a better life and do better.
"At the moment we are seeing the gap between those who are wealthy enough to be privately educated and the rest getting wider, and we are seeing the working population working longer and longer hours having suffered huge wage compression over the course of the last 10 years with their household bills going up.
"What we want to do actually is to genuinely address the cost of living, and to address social mobility."
There would be "no tax on the minimum wage" - although he did not specify what the minimum wage would be.
"We are going to rethink the tax thing. I think that was badly explained. What I can tell you for certain is that our biggest tax objective in that next manifesto will be no tax on the minimum wage. We have got to incentivise people to get off benefit and get back to work," he said.
Farage also said he supported a "top rate of tax of about 40%".
"I think a top rate of tax in this country of around about 40% is the one that will bring the most revenue into the Exchequer," he said. "I think that's what we will conclude. Anything over 40% and I think you start to see people go overseas."
Asked whether there would be a grammar school in "every town" if Ukip were in power, the MEP replied: "Absolutely.
"The lack of social mobility in Britain is quite shaming, and selective education is one of the ways to give bright kids from poor backgrounds a real opportunity."
Farage conceded that "savings" would be needed, suggesting he would take a "chainsaw" through middle management to make the NHS more efficient - although he said the party would not "necessarily" remove ring fencing from the health service budget.
"What we have got to do clearly is re-prioritise what the NHS does," he added.