Cooper lead Pools to the play-offs this season, before dramatically leaving the North-East club ahead of their semi-final tie with Tranmere.
And he is confident that his experience in League One will help the Gills, who were relegated from the Championship this season, come August.
He said: "When I took the Hartlepool job we were everyone¹s favourites for relegation, but it didn't turn out that way.
"I've had the experience of working in this League. It is a hard League and there are a lot of strong teams in it.
"I would love to achieve promotion, but it will be a hard season. If the fans see a team which works hard and competes though, then they'll get behind that.
"We will get the team ready, strong, fit and organised, and with the quality already here push as high as we can."