both manual and strategy guide are in the FAQ sub-forum (at the top of the page). In theory the manual tells you the mechanics of how the game plays and the strategy guide gives you practical play ideas (in reality there is an overlap between the two). In truth, after several patches, the manual is only useful for orientation and as an indication as key mechanics have altered, but well worth a read to understand the main mechanics.
beyond that ask on the forum (you'll get good answers) or read some of the after action reports (again a link to the relevant forum is on this page), lots of good ideas and practical advice in there two. Read the unofficial guide to Republics - utterly key to understanding how to deal with the populist menace.