How governments can encourage healthy markets...

That enhance:
Market competition

leading to lower prices, higher quality and greater product innovation.

Market health
Qualities may include:
Relative stability in the market, in terms of output quality, quantity and price, firms coming and going and ongoing sustainability of the market.

To achieve these goals:

No unsurmountable barriers to entry should exist, barring outside entries into the market.

If necessary, finance should be available to enable sound economic projects to go ahead.