What is a functional strategy for creating keyword lists and doing keyword research?

use aso keywords tool and google keywords planners

Some sources and activities for inspiration when you create your keyword lists: 

• brainstorming sessions with your team
• asking users what they would search for in the stores to look for an app that delivers the same game experience
• seasonal keywords (Valentine, Halloween etc) 
• trending keywords
• your app's reviews

Competitor's metadata can give some inspiration and could be good to track, however, avoid using obvious competitor names as keywords, as this is considered a violation of the store guidelines and might cause your app or updates to be rejected. Research their use of keywords in the fields that are visible to you in the store pages. 

The ASO tool that we are currently using has a feature that provides a list of all the keywords that we have been ranking for. I select keywords from this list that have a medium to high search volume.

Perhaps the most important source for keyword suggestions is your paid UA campaigns. Pick the keywords and search terms that convert well.