Started out farmer lvl17 now getting mildly beefy and excited to fight. How do you fight and or should..

You can change your class by paying or you upgrade to lvl 19, then it’s free. Check your class hall, maybe you still have a free ticket to change class.

Any class can fight, you don't need to be a raider. The raider class has some small buffs though and the marching speed reduction for the farmer is a minor hindrance.

To fight you just need to find and attack other players. Look for enemies that are not shielded. It is best to check with your alliance in case any other players / alliances in your state have an address meant not to attack. The best opportunities are during cross state events. Clash of zones weekend kill events lets you travel to another state and attack players there for points as well as resources.

Talk to your alliance and get their advice on who is a good target.