given your situation, yeah sure stick to live food. dont feed too many FW feeders though. you should stick to mainly various SW feeders, and FW as much as possible. if you want you can always try better suited frozens like krill or shrimp.
definitely look into an upgrade for this guy. I would keep it a species only tank. so no tankmates. corals are fine.
remember that if you spook these guys sufficiently, they might ink and crash the tank. have a plan ready in case this happens.
lol i b*tch if my friends even suggest getting me a fish without my knowing about it. this is an example of why. a cuttle is NOT a good choice for a first ceph and a ceph is not a good choice for any beginner. like opcn, you'll be lucky to get a month out of him. experienced ceph owners rarely get them to make it past a year. still, he really is a cutie! ive always wanted a cuttle myself, but im not confident enough in my abilities... yet.
edit: i would not recommend seahorses to a beginner either as they require special care and have a pretty bad mortality in home aquaria.