Reputation

There are two types of reputation. Military, and Commerce. The combination of these two values will determine your Level.

Military Reputation
Military reputation is obtained by fighting other fleets. Players, Unicorn and NPC. Or by occupying other player Cities.

The amount of reputation gained is based the number of tonnes of the enemy fleet you destroyed, or the size of the city (Population) of the occupied city.

A good way to increase your military reputation is the NPC Zone due to the large amount of NPC Fleets.

Commerce Reputation
Commerce reputation is the reputation you get from selling Resources and Parts to other players and the Empire.

However, you only gain reputation if your max profit increases. Simply put, if you spend 0g on buying materials, then anything you sell will increase your reputation.

If you were to buy for 50g worth of materials, then your reputation will not increase until you've made back those 50g as profit.

Note that you never lose reputation. It just stops going up until you're making a profit again. This is to prevent two players from selling materials to each other, and constantly gaining reputation from sales.

You can find your profit margin in the lord info screen. In order to gain reputation from sales, simply make sure your Current Profit and Max Profit are equal if you are trying to gain reputation from Commerce.