Prime Minister Brian Mulroney set Canada on a more conservative economic course today with a probusiness budget that stressed private investment and reductions in government spending.

The budget message, the first since Mulroney's Progressive Conservative Party took office in a landslide election victory in September 1984, reflected a widespread conviction that Canadians want an austere, belt-tightening fiscal approach to invigorate their sluggish economy.

"We will promote growth and job creation by encouraging private initiative, improving government effectiveness and controlling our national debt," Finance Minister Michael Wilson told the House of Commons.

The budget contained no significant increases to beef up the armed forces.

The tone of the economic message moved Canada further away from its position in the years of former prime minister Pierre Trudeau, whose nationalist economic policies and expansive social programs often alienated U.S. businesses and government.

The budget, which puts forward the economic program for fiscal year 1985-86 and years beyond, contained wide-ranging incentives for small business and investors, including a partial elimination of the capital gains tax that will cost Ottawa significant loss of revenue -- up to $1 billion -- in the next two years.

The thrust of the Mulroney government's economic approach echoes that taken by the Reagan administration -- that leaving more money in the hands of investors and businesses will lead to economic development creating jobs to alleviate the nation's worst problem -- unemployment.

Despite real economic growth last year of 4.7 percent and projected growth of 3 percent this year, the unemployment rate is still running at nearly 11 percent.

Like President Reagan, Mulroney has been severe pressure, particularly from the business community, to trim government spending to reduce the federal deficit, which is put at $25.7 billion for this year.

Wilson said today that he would trim the budgetary deficit by $3.1 billion to $22.6 billion this year and achieve further reductions in the next fiscal year.

To do so he proposed higher taxes on a variety of items including cigarettes, gasoline, alcohol and pet food. The government will also sell off some of its many government-owned corporations.