It's always good to break the 30 marker down into two sections:
18 marks for KAA (Knowledge, Application and Analysis) and
12 marks for evaluation. You should have roughly 3 points with 2 evaluations for each. Use diagrams if it will bolster your analysis, otherwise don't use them as they could waste time if inappropriate to the question.
1) Your first point could discuss supply side policies used to increase aggregate supply in the economy and thus economic growth. An example would be an increase in Education & Training, say "building 1000 more schools" or offering more apprenticeships (something the Lib Dems are trying to implement:
http://www.bbc.co.uk/news/election-2015-32364053). More education and training in the UK economy will mean students are better-skilled, and go on to gain better degrees at university, leading to highly paid jobs, leading to high levels of consumption (biggest component of AD) which in itself will lead to more economic growth; highly paid jobs means more income tax is paid, for example, meaning the government benefits from increased tax revenue, possibly reducing the budget deficit. Your evaluation for this question would be: There is a huge time-lag until the students start working. Also, in the short-term, the government loses out from increased tax if the students were to get basic jobs once leaving school. This point is great to use a LRAS/AD diagram, which can also be evaluated. On the diagram, have on your x axis, output, and on your y axis, price level. Draw your LRAS curve and draw up to four AD curves showing different economic situations from increased education and training. For example, if AD increased to AD1 this would cause an increase in inflation as P moves to P1. Moreover, increased AD reduces spare capacity in the economy as we get closer to YFE (full employment). Then to relate it back to the "promotion" aspect of the question, state how increased employment from increased education and skills will increase investment into the UK as the country is seen as being more stable then before and a lucrative nation to invest in; this will better the UK's reputation and advertise the new found increased economic growth the country is now experiencing.
Other evaluative points:There is a high opportunity cost for the government, especially in the run up to the 2015 UK Election.
Also, we assume people who are educated more will get higher level jobs. However, this depends on what subjects they study, as some are notoriously more facilitating than others, so will render a higher-paid job.
Now you need points two and three, and evaluations for both, and you could be heading for a 28+ mark essay!