I am a raider. but am only able to raid 198k of money. Which upgrade (or upgradeS) do I need to research..

When you raid the amount you get will depend on your APC's load capacity and on what the enemy has available to take. If the enemy has ONLY lots of money then you will just take money, but if they have a lot of food then you will take mainly food. Ideally you want an enemy that has more money than other resources.

You can increase your load capacity by upgrading the barracks and hero skill upgrades to allow you to take more troops. And research in the APC research trees for 'Load Improvement'