George Osborne was clear about the headline he wanted from this budget – so clear, in fact, that he wrote it himself. His budget would put "fuel in the tank of the British economy", he declared, ensuring no one could miss what had been the climax and chief surprise in his speech: a postponement in a planned rise in fuel duty coupled with a 1p cut, to be felt at the pumps that very evening.

His hope was that the move would ensure a warm reception, especially as, in a nicely populist touch, the price cut will be funded by the big North Sea oil companies. A crowd-pleasing rabbit pulled from the hat, a windfall tax on mega-corporations – why, it almost reminded you of Gordon Brown.

Though designed for immediate consumption, the fuel move could have a lasting political effect. For it signals an end to the first phase of this government, in which it argued that the country was on the verge of bankruptcy, that there was simply no money left. By giving a tax cut, Osborne has signalled that he does, in fact, have a degree of discretion: he had some money to spend and he chose to spend it helping motorists. Now those campaigning to save a local library will be able to say: why couldn't you have spent that money on us? In a small but clear way, the terrain of political battle has shifted.

Osborne's goodies were not limited to the garage forecourt. He raised the tax threshold by an above-inflation £630 and gave help for first-time house-buyers. The bigger picture was a raft of pledges to make Britain a proud manufacturing nation once more. He beheld a "march of the makers" – a phrase that clunked as heavily as a balloon cast from British-made lead.

These announcements will be welcome but they have an enormous job of work to do. They have to somehow mask the large patches of gloom that blight the wider economic picture, not all of which the chancellor could keep out of his speech.

The darkest are the growth figures, which he had to revise down yet again, the estimate for this year falling to just 1.7%. Seized on by Ed Miliband in an impressively feisty response, this is the potentially fatal weakness not only in Osborne's plans but in the government's entire strategy: what if the severe austerity programme aimed at wiping out the deficit by 2015 hollows out the British economy in the process?

The opposition has been pressing that case, insisting that the slash-and-burn Tories have no plan for growth. The effort was not in vain: the chancellor clearly felt he had to come up with something, coming over all Michael Heseltine with promises of enterprise zones and help for startups. His talk of rebalancing a lopsided British economy, too centred on the City's financial engineering and not enough on "making things", could have come from any Guardian editorial of the last 30 years.

Whether it convinces is another story. For whatever giveaways the chancellor mustered are dwarfed by those changes that did not appear in this budget but which are becoming more real by the day. A penny off petrol is nice – but doesn't amount to much compared with January's VAT rise to 20%. The change in tax allowances are better than a poke in the eye – but barely relevant to the family about to lose a long-cherished public service or tax credit. What Osborne announced is only a relatively small part of what this government is doing to the pockets – and lives – of the people of this country.

Even within the budget there was much that will grate. Doubling the planned cut in corporation tax will be hailed by the CBI as action for growth, but plenty of voters will regard it as help for fat cats. They'll have noticed that while non-doms got an increase in the levy they have to pay – pocket change for most of them - the chancellor also promised to leave them alone for the foreseeable future. Even the much-ballyhooed tax on private jets is not immediate: the chancellor said merely that he would "seek to" make the Learjet classes pay their way. The result was that when Osborne repeated his troubled slogan – "we're all in this together" – there was hollow laughter from the opposition benches.

As always, the true test of any budget is not the immediate reaction, but the judgment delivered once the numbers are crunched. To take just one example, from now on the personal tax allowance is to increase not in line with the cost of living, but with the less generous consumer price index. That could eventually wipe out the increase in the threshold.

Osborne will be judged on the larger gamble he is making with the British economy. And in that story, this budget will be but one small chapter.