Pick up what ever ID book your using and look though it. Family tendencies are always good to know. Some broad statements like as far as I know there are no poisonous grasses (Poaceae) is pretty good. Most non-vascular plants are pretty benign, but often have a lot of abrasive fibers (some made of silica). Then again these broad strokes can be dangerous. The Apiaceae (or Umbelliferae) family contains fennel, carrots, and Socrates favorite tea- hemlock.

I once thought about becomming an ethnobotnest. But things change.

Kudos to you and your quest. It would be interesting if you actually tried each plant you identified for is use (less the poisons). At the very least keep a good journal with pressings and drawings.