Several problems here:
1. The people in the database did NOT opt in to receive offers from you. Whatever you send is SPAM and violates the Can SPAM act and the terms and conditions of most reputable casino affiliate programs.
2. The number of SPAM Cop complaints you will recieve will make it necessary to find a mailing company offshore whose IP range isnt blocked. Most of your email will be blocked after several mailings making the returns smaller and smaller unless you continually switch mailing firms.
Well over 97% of the traffic you receive will be fraudulent and produce 0 conversions. If you dont believe this then you havent done much PPC advertising offshore.
The people who recommended Organic Search SEO know what they are talking about and arent merely speculating.