Launching the party's Welsh manifesto in Talgarth, Powys, Kirsty Williams said it had "opportunity at its heart", with  more money for public services.
Higher spending on English education would mean an extra £150m for Wales over the next five years, she said.
The Welsh NHS could also get an extra £450m, Ms Williams added.
The Welsh Lib Dems would seek to spend the extra money for education on the poorest pupils.
Ms Williams said the introduction of the Welsh pupil premium "has been my proudest achievement".
Additional Lib Dem health spending in England would also generate an additional £450m for the Welsh NHS, Ms Williams said.
The Welsh government would decide how to spend the money, but the Welsh Lib Dems would urge it be spent on their health priorities of safer nurse staffing levels on hospital wards and equal status for mental health.
The party also wants to see the the full implementation of the Silk Commission proposals on further Welsh devolution and a "proper fair funding system for Wales".
The Lib Dems have already announced plans to make it easier for young people to rent homes and review the way the Welsh government is funded.
Elsewhere on the campaign trail on Wednesday, Labour has announced that firms getting major Welsh government contracts will have to offer apprenticeships.
Plaid Cymru argued that "equality of funding" for Wales with Scotland offers the "best hope" for protecting public services such as the NHS.
The Conservatives are focusing on their manifesto commitment to pass a law to guarantee a Tax Free Minimum Wage.
Launching UKIP's manifesto, party leader Nigel Farage promised to reform the formula used by the UK Treasury to decide the budget for the devolved governments, to give Wales and England a "better and fairer deal".
The Liberal Democrats have shown they have "the mettle to take the tough decisions but the right decisions" in government, their Welsh leader says.