Post your offer reviews and make them interested in your offer as you can tell them like " hey Guys, We are gonna launch something so interesting and useful for you guys.. this is quite unique than others" and all that. Then post a link and tell them to read the full article about that product.. Make sure the site you wanna use looks professional.. and thats how people will never have a time to think you are spamming them...
So, they will surely follow you and their other followers will also start to follow you..
Informative Posts are better than Interesting Posts.. Because, Interesting Posts could go out of the line from your business purpose, but Informative posts will be based on your Business Issues.. Thanks..