How can I edit some files to make it better?

[Seasoned Alcoholic]

Before you mod any of the vanilla text files, create backups in case you make a mistake.

As Ludens says, you can counter squalor by editing building bonuses in export_descr_buildings.txt @ C:\Program Files\Activision\Rome - Total War\Data directory. Look at how the default buildings use health / growth bonuses etc, then simply copy, paste and adjust as necessary.

You can also edit descr_regions.txt @ ...\Data\world\maps\base. The top of this file tells you which line the base farming level is for each region, simple edit as necessary.

You may notice the grain resource in descr_regions, this also boosts population growth considerably. Some regions don't need this (EG Egypt x 2, Carthage x1 etc) because these regions can create unit after unit after unit without feeling the disadvantage of population loss.

To delete grain resources, you need to open up an imperial campaign (start a new one if necessary). Now open the console (RomeShell) and type in toggle_fow, which makes the whole map visible. Browse to a grain resource (the wheat icon) in a province and put your cursor over its location. Now, open the console again and type in show_cursorstat. This gives you the coordinates of where the resource is located on the campaign map, write these down if you need to. Close down RTW and exit to desktop.

Now open up descr_strat.txt @ ...\Data\world\maps\campaign\imperial_campaign (maximise the text file if necessary). Now, scroll down a bit and you should see this:

; >>>> start of resources section <<<<

This is where all of the campaign map resources are listed, with their coordinates. Hit Ctrl+F to open the search tool, and type in grain. Now cycle through the grain resources until you match the coordinates to the ones you have written down, delete as necessary, save and exit.

[Seasoned Alcoholic]

Forgot to mention diplomacy, so I'll start a new reply rater than edit the previous one which is quite large

Diplomacy can be modded to an extent in RTW, you can mod the core attitudes and faction relationships per faction against all of its rivals. To do this, open up descr_strat again. Now hit Ctrl+F and type in diplomacy. You should see the following:

; >>>> start of diplomacy section <<<<
;DS_ALLIED            = 0    
;DS_SUSPICIOUS        = 100
;DS_NEUTRAL            = 200
;DS_HOSTILE            = 400
;DS_AT_WAR            = 600

These are the various tiers of attitude towards other factions. A numerical value is assigned to represent a particular attitude. These can be increased in 10's at a time, not sure if you can have say 123, you would need to use 120 or 130 etc. After the numerical description, there are faction names that are tagged against the numerical value.

You will see that the Roman factions use -10, probably because they are all allied from the start and cannot break their alliances until the civil war erupts. As you can see, some core attitudes (EG 410) are unecessarily high, mod these down to something more appropriate. Try using neutral (200) or in between neutral and hostile (300), I've found the AI is more willing to work with you in diplomatic negotiations, EG signing a ceasefire. Not sure if they will honour alliances, but at least it prevents bias each new imperial campaign.

[Cras]

you can also NOT build the irrigation thingies that improve the growth of a city...

and... pomp out an army or 2... and then you have enought to leave and retake it and make a LOT of money. The right religion often helps too.. did you check the reson of the squaler??