Promote growth and reduce waste.
Ditch HS2, the principal argument for it was an increase in capacity, the numbers WFH are only going to increase so upping capacity on routes that already exist is not required. Much of the sunk costs were spent buying land so aren't wasted. Do spend on infrastructure elsewhere.
Reduce planning requirements, which would increase the number of houses built, reduce prices and give people hones that they want to live in.
Reduce stamp duty, it's a massive drag on the economy and leaves people stuck in homes they don't want and stops people being able to move to where the work is.
Reform the business rates system which punishes high street shops and reduces capital spend and could be done in a way that captures the tech giants without scaring away investment.
As several people have said legalise and regulate cannabis, I'd also add prostitution to that. It would bring in large tax receipts, reduce criminality and the cost of policing.
Reform much of the state and get rid of many quangos, they've been used by all parties as a way of politicians avoiding making decisions. Public Health England and Health Education England cost £3bn between them, what's actually been achieved for that money. PHE hasn't had a good crisis, despite a coronavirus pandemic having been at the top of the risk register for years.