I put some notes on some of the items it will help you through out the game.
always remind :
Against Phantom assassin, keeper of the light , and other agility heroes that you will expect to build butterfly.
You can either build basher and keep hunting them, or if it's too late never go for basher and go for Monkey King Bar.

How to be the best assassin :
1. Always Spot your prey
2. Never engage in fights too Fast
3. ^ Look Around if Your prey Has some allies.
4. Don't get overconfident, always buy gem.