It takes a troll a long time to recover from a swing. If you don't have a shield that can stagger them when they attack you can dodge and then fire an arrow, dodge fire an arrow, repeat until troll dies. Pick up coins and troll hide to work on the troll armor set. Trolls are weak to piercing damage so flint arrows on trolls works well.

Fight in retrograde. Back off at walking speed. When the troll swings dodge and fire an arrow. Use the terrain to your advantage, dodge around large rocks particularly the standing stone types, and use them as partial cover.

When graydwarves swarm use fire (torch/flaming arrows) they are weak to fire and run from fire and camp fires. Fight them in retrograde too. Get a shield. When they attack block and stagger them and swing once, repeat and eventually you will have chewed through the swarm.

Keep killing the trolls. They all spawn near points of interest (stone towers, copper deposits etc.) Where ever you find a troll there is something worth investigating especially early game. Once you've killed a troll it takes anywhere from 3 game days to one game week before they respawn in that location.

Don't forget to use sneak. Sneak into bow range and make your first shot a surprise attack. The troll will suffer quite a bit more damage with that first shot. Avoid the 2 star trolls when ever possible. They are hard to take on even with good gear.