Most games have a good RPG feel to them. My advise would be to play a few games of single player and get a good feel for the game.
There are hundreds of posts about tactics and strategies to beat the AI so you will have plenty to read.
As for good add on mods, well the Image Mod is a must have, as is the FQM mod. The Formations and Anthology addons are also great additions.
Those can all be gotton from
www.spaceempires.net