Two pronged question here folks. First, I’m playing a variant human arcana cleric in the Greyhawk setting. He follows the god Celestian.

Here’s my basics:

8/14/14/12/16/10

Feat: magic initiate druid (shillelagh)

Question 1: what other druid cantrip and what first level druid spell help this character the most?

Question 2: I can’t decide between booming blade or green flame blade. I’ve read that booming blade is generally a better choice, but I’m not sure I understand why. Also, the arcana clerics level 8 ability favors green flame blade. Or should I just choose both?

Celestian is the god of magic, wanderers, and astronomy.

Question 3: how can I beat represent knowledge of the stars and celestial bodies in D&D? My character is proficient in history and arcana, but should there be some skill for using a telescope?

Thanks!!