Predecessor Builds > Rampage > Carry Jungle!
Rampage's abilities scale really well off of pure attack damage, so getting Basalisk first is key here. His base health is so good that you don't really need to build tanky early.
Hitting your boulder throws is very important. The stun duration is crazy long and does good damage too. If you can land every throw it will be easy kills for you and your team, practice it!
The route I use is Red->5 minion camp->2 minion camp-> gank mid from behind-> steal their blue -> gank outside lane
Invading is dependent on where the enemy jungler is and how mid gank went etc.
If you are getting the majority of the kills early, go for Overlord second item. It will allow you to clear camps really fast and still keep up with ganks at the same time. Otherwise, go tanky earlier with fire blossom. This is because you need to switch your role from being a solo carry in fights to supporting and tanking for the players that are getting kills. They will have more gold.
As always, the Jungler should always keep track of when Orb and Dragon are up, go for them if the enemy jungler is dead or mid and offlanes are backing/dead. Never start them when all enemy players are still alive! You will not be able to kill it fast enough.