Proper way to index table columns which can be filtered in multiple ways
Every index adds some value, and comes at a cost.  It's up to you to figure out whether the value outweighs the cost.  

In order to get a handle on the value, you have to find out which queries use the index, and how much slower those queries run without the index in place.  

In order to get a handle on the cost, you have to find out how much slower updates run on the underlying table, and how much space the index itself takes up.

There are tools to help you evaluate these facts.  Facts are objective.  The value you place on them is not.  How much value you place on the query speed up and how much cost you assign to the update slowdown depends on what you are trying to achieve, and on your relative priorities.  That's up to you.