Team pushing is okay if the enemy is ahead if you manage not to get killed. It forces them to react to you, but if they decide to ambush instead of defending their reaction can kill you, or not depending on how you handle the ambush and how good it is. Of course, if your outer tower is still up all you need to do is ward the lane side and team push then they usually wont able to ambush you unless theyre really clever or really fast. If your outer is down, however, then its a bad move if all you have in mind is push.
Answer: if outer is down never push unless you have a plan to deal with their teams counter push because theyre ahead and they have a raw strength advatnage, if you dont then farm your jungle and lanes (if youre team isnt coordinated you can be forced out of the jungle and lanes, though), but you dont always need to split and farm you can sometimes group and roam the jungle, catching out of position enemies, or if you dont meet anyone roam all the way till their buff and steal it, using wards to provide early warning of counter steal and an escape route (always upgrade trinket at lvl 9).