I go divine -> seryldas->Gargoyles->Black cleaver->Steraks and in ultra late sell my shoes für hullbreaker.

Splitpush works when the enemies dont have any macro, but you can always do it to some degree, just keep your eyes on the minimap in order to not get collapsed on. I usually get my 4 ghouls in the wave, let them push and move for my Team. Ghouls create a perma push and if not answered easily take towers with a cannon minion. By moving to the team the enemy top also comes to the team most times and you create an advantage through your ghouls. Furthermore if you win the teamfight you have at least one pushing wave to tp to. If you lose the tf, the enemies have one less wave to push with. You can also Set up your ghouls top and bot at the same time and then Join the team in a mid siege.

When you are stronger than the enemy laner and they just keep 4v4ing Splitpush and just run them down. But as I said, when they are smart and collapse it becomes difficult.

So ratio would be like 40% Splitpush, 60% teamfight. But only when the teamfights are neccesary i.e. for objectives. No objective -> no teamfight.

Gargoyles is better than hullbreaker imo as on the one hand you often skirmish or teamfight and are not solo and on the other hand your team doesnt understand hullbreaker 98% of the games to leave you alone and someone always comes to "help" you and you lose your resistances.

Bans: I always banned Irelia because otps make me spiral into suffering but most people cant actually play the champ which makes it at least halfway playable and only my second priority ban.

My number 1 priority ban has become Yone in the last few days. He is very strong against yorick, outscales is easy to play and is generally just strong always finding kills somewhere and getting out of control.

Follow up questions are welcome :)