I would much rather dream big about the ways I could make my city and the world a better place through carefully selected charitable enterprises, than "dream big" about a too-big house, paying people to cook all my meals (that sounds awful, actually, since cooking is one of my favorite hobbies), shopping at the mall every week (!!!) - basically all things that would make me significantly less happy, not more. The whole point of this site is to live your best life, and the fact that best =/= expensive.
So much this. Buying yourself shiny shit seems pretty unambitious to me (unless your ambition is to turn yourself into even more of an environmental catastrophe than the average American/Western European).
Sure, I'd pull the trigger on a few capital intensive things that we're currently holding off on - putting enough solar PV and storage into the house to be more or less self sufficient, seeing how far it could be pushed towards Passivhaus levels of thermal efficiency, extending a little to prepare for the space the kids might 'need' as teenagers.
I'd probably get rid of the car, because we'd no longer be balancing frugality against environmentalism in the stupid situation where it's cheaper to own a car for a whole year than to either hire or take the train for a handful of family trips. Same for travel - we'd have time and budget to cross Europe by rail.
Something like a million GBP in the bank would cover that and the rest of our lifestyle indefinitely with plenty of headroom.
But then just start to dream...
- Our neighbourhood politics is dominated by an argument over plans for a supermarket on the high street on what is currently a church and a pub. Church wants to sell up so they can build bigger and better on a cheaper site, Residents Assoc is massively opposed because they're pissed about the pub. I'm indifferent-to-slightly-against the supermarket, but mostly frustrated because it's basically impossible to get anything else on the local agenda. Given a crapton of money I could just buy the damn land and maybe build something with real community value, then we could all move on to more pressing issues (except supermarket MegaCorp, but screw them).
- Our local library is on the verge of closure because the city council is broke. Its (the library, not the council) operating budget is maybe a few hundred k per year.
- I can think of several places where poor planning decisions have led to problems with foot/cycle permeability (and hence people driving everywhere), but this could be fixed by giving homeowners ridiculous cash offers to cede a few metres of garden to the city.
- I could bankroll the renewable energy R&D programme that I've been working on for the last couple of years but which we didn't get the next round of government funding for. Hell, I might even fund it anonymously and just stay in my job to work on it.
I could go on. The tricky thing would be balancing what I put into these things against the valid case for throwing it all at Givewell/Effective Altruism.