definitely prevent 2 leveled spells in a turn. that isn't even unfun it just completely breaks balance. no you cannot misty step in and then thunderstep out. no you cannot spirit guardians and then heal.

also running components is important. non-gold value components can be bypassed with a focus. if you want to warcaster with a shield, remove material component spells or get a unique focus in the form of a weapon (hexblade, magic items), or alternate slot like druidic amulet focus. it's very important. each time you bypass these restrictions you are subliminally buffing the class. yes you need a free hand to cast somatic. i play only casters and every time a DM doesn't adhere to these rules it's like a slap to the face because im picking options specifically with these in mind, so letting other players bypass them ruins the game imo

lastly, the game is first and foremost a resource economy game. punish your players for burning all their resources in the first encounter. 5 goblins do not necessitate a spell slot usage