bro adwords is the best option to find out a keyword, i'm also a owner of gaming blog. and according to my experience adwords is the best !

What are you trying to sell or market besides it being in the football manager niche. Use adwords to then target this group while thinking about how much time you are willing to invest in this project. Once you've done this you willl have a clearer idea of what you need to do.

Use the adwords keyword tool. Me personally, I use the exact match option. When you use google adwords keyword tool, put your football manager as the word or phrase. Make sure to select the keyword ideas tab instead of ad group ideas. Football manager should come up with 301,000 global searches and 4,400 local searches. Under your main keyword phrase "football manager" you will see 100's of keyword ideas.

Google adwords keyword tool is all that you need. It works great once you learn how to use it properly. You will probably get most of the traffic from Google so is very good to work with this tool. Here you will find more info about using it:

How to Use Google Adwords Keyword Tool - Step by Step Guide | eHow.com

Using the Google Adwords Keyword Tool for SEO

I think this is a wrong post for forum since this is offline marketing.
Shall be in the online marketing thread isn't it?

Google keyword tool - learn it, live it, love it

haha its great

As what others have already said, use the Google Adwords tool. It will give you the right suggestions for your chosen keywords. You can also view which keywords you would like to target that are high impact but with low competition.