I'll be using the US for my numbers and policy.
First up, a negative income tax.
10,000 dollars a year basic income at the federal level with states and cities having additional programs to cover the differences in cost of living across different areas. Eliminate other welfare programs like SS and need based welfare.
Using this calculator (so numbers are hypothetical)https://dqydj.com/scripts/fullhtml/base_2015_negativeincometax.html You could get that with a 20% effective income tax rate (a tad less than we have now) and it would be deficit neutral.
I'd hike the effective tax rate to 30% to get a few hundred billion dollars to go into other programs and balancing a budget.
Add a VAT tax with rebates, the stuff I found on this was for a 5% vat and would raise 350 billion.
Carbon tax (and in general get a bit liberal with pigouvian taxes), the CBO estimates that over a decade it would yield 1.2 Trillion dollars.
Universal healthcare. Basic coverage with a single payer insurance program with a deregulated free market in additional private coverage. Estimates on the cost range but it would probably be around half a trillion extra a year which would be what the VAT and income tax increases would go to.
Those are my big ticket things.
Other stuff I'd do, double the budge of the NIH, NSF, NASA, and other various research programs and institutes run by the US government.
Launch a full scale plan to study and revamp the US education system, modernize it, and steal all the good ideas from other countries.
Increase job retraining program funding.
Take a look at labor regulations (with the basic income a lot of them become unnecessary or need to be modified to work with the new conditions).
Revamp the college loan system, bring private loans under control, take back control of sally mae, make it so you can discharge the debt in bankruptcy, etc. I don't think it's unreasonable for society to invest in better job outcomes and then at least get a modest return on that investment as long as it goes to public coffers and not private ones. Reevaluate our various regulations on the college sector.
Perhaps free community college but I honestly believe that free university is a middle class boondoggle because the greatest costs of going to college is having to not work or work less for a few years and still pay for rent and food. Not an issue for the middle class but this is a huge burden for the poor and is the greater cost of entry than tuition IMO. However that attitude is up for revaluation with the basic income which would do a lot to lift that part of the burden.
Legalize, regulate, and tax drugs.