What could cause poor circulation and tachycardia?

Chicken or egg? Depends on what you mean by "poor circulation. Rapidly beating hearts may pump blood inefficiently, reducing circulation in limbs & organs thus causing symptoms & complications. Or, clogging and hardening of the arteries may reduce blood flow to the heart, causing irregular rhythms like tachycardia. There are other more complex diseases that can also cause both.
Multiple. Poor arterial circulation from smoking and atherosclerosis. Poor venous circulation from deep vein clots tachycardia is secondary to a huge list anemia emphysema cardiac etc.