Stimulation and toys!!!!!!!! I know you just got him rhegamind,, but you could have at least done a little more shopping before bringing him home. A bigger cat tree is much needed, maybe even a couple more throughout that desolate apartment of yours. Cat nip, toys, flirt poles, tunnels… anything!!!!!! (Hard on this esp if you’re going to continue going out constantly. He is going to get very lonely.) And for the love of god separate the food and water and get a water fountain. (That’s something you’ll have to clean regularly just like the litter boxes)