There is no mystery or complicated plan with roundabouts.
It is a junction.
Use the same lane discipline as if it were a normal cross road.
Right lane turns right or straight on.
Left lane straight on or left turn. (Third exit for the pedantic!)
Give way to
all traffic from left before entering.
Before entering roundabout signal your intention to turn right or left (Third exit) no signal for straight on.
Do not change lane in roundabout.
Signal right after you have passed the exit before the one you want.
So simple.
Except in The Villages!