When checking for interests for a new campaign:
I want to target people that had an interest in games similar to the one I want to promote.
Let's say that there was 40k people that had an interest in the game I want to promote.
-Is it wiser to target games with double that number, let's say 80k? thinking that my not have heard yet on the game I'm looking to promote?
-Or should I target games with half that number, 20k? My thinking is that those people already know the bigger games and maybe looking for something else so maybe it is not a good idea to target those people?
- Maybe I'm over thinking the whole thing? 
Would love to hear what is your strategy when going for gaming campaigns on Facebook!
Hey Omrikios,
Honestly, you will never know unless you test. So, i'd split test both.
Make an adset targeting larger audience interests vs smaller audience interests.
Personally ... my opinion is that you'd be fine bundling everything into one adset (but you never know).
One strategy I use is called "Affinity Targeting" and it gives me 100-2,000% ROI
campaigns and extremely high CTRs.
Try using the FB Audience Insights Tool.
Let's say you are marketing a game similar to clash of clans.
You would go in to Audience Insights and in the left column "interests" type in "clash of clans"
It'll pull up results and go to the top tab "Page Likes" and look for any similar page likes that
have an Affinity ranking of 10x or more. It's really good if you can find them at 20x +.
Here is a screeny:

Hey Adrian,
That was some killer advice there. I'm already using the FB insight tool and the type of ad i'm running is a boosted video post about the offer I'm promoting. The thing is that the angle I'm taking is targeting a famous a game and using the famous "this is better than this" method so bundling might not work. but testing is the way to go probably just not in ad sets.
Thank you man!
P.S. Added you on FB
Nice - I've been testing video ads lately myself!
In power-editor there is a feature that allows you to capture all
video "viewers" in a custom audience.
If you aren't already utilizing that feature I def would. That way
you can go back and re-target them with a link-ad. BOOM!
That's awesome (capturing video viewers as an audience), couldn't find how to do it yet.
Also, I saw on another post that you are aiming for a larger audience when targeting your ad. For targeting people that like a certain game in a certain country, in my example I targeted people from the UK that are interested in "tribal wars" game which is similar to the game i'm promoting. There aren't a lot of interests you can target in this case: I limit my self to gender country and people that had an interest in tribal wars. that gave me 18,000 people.
1. How would you go and make this audience larger while keeping targeted.
2, I found that just targeting people that liked "Tribal Wars" still wasn't targeted enough because maybe they were not actually playing the game so I needed to go even narrower.
What would you do guys?
And thanks Adrian for the help so far
Wow, that's a killer tip on capturing video viewers as an audience. Thanks - I'm off to implement that just now...
Did you find how to do it yet? It seems Facebook let me create an audience only for people clicking for the website no?