1) Adequate investment in infrastructure to maintain and grow with demand.
2) Critical Govt services - Health, education, justice, defense
3) Social spending
Any 2 can be prioritised as per the political will of the party in power, but this will leave the 3rd deficient of funds to make any real impact. Which 2 are prioritised really depends on the overall leaning of the political party in power. You can't keep dividing up the $ and expect all areas to perform.
Its not necessarily the Govts position to grow the economy, that should be left to the market / businesses, but it is the Govts responsibility to create an environment in which businesses can grow (export markets, access to resources through proper legislation etc).