It sounds better when you include “of” here. It’s a good habit to get into because down the road there will be situations where you will think it’s okay to leave out the preposition when in actuality it won’t be. Build good habits now.

both sound fine, both written or spoken. But please don't use "like". It's like a word that like young like people like use like a lot to like punctuate their like sentences without realising it and makes them sound like dumm

I would say that in speech it’s not essential but written down the preposition should be included. Using “like” sounds more natural to me, but that’s just my opinion. “Of” is correct.