So new player here. Does the druid get access to all spells listed in his spell list (PHB p. 208) he spell slots for? Because some Circle Spells are already in that list (e.g. Barkskin) and some are not (e.g. Spider Climb).
This has always been the difference between Divine magic ( Druids/Clerics for example) and Arcane Magic (Wizards/Sorcers etc.) Divine Casters had access to all their spells at the appropriate level and had to choose which ones to memorize daily. Arcane casters could only prepare spells they knew and had recorded into their spellbook.
So if you have access to 2nd level spell slots, you can choose from any of the 2nd level druid spells, only preparing a number of spells as detailed in the above post.