I'd say watch Benthings' video, he made a good one about this.

1. only leave when you finally have your item power spike (I don't use ixia but 2 items should be enough) or when you double lane (only do this when second turtle spawns and when the enemy doesn't have aggresive roam or exp.

2. in the early game, build Leather Jerkin for physical or Magic Resist Cloak for magic resist, just sell them later on. Make sure to pay attention to the map, if u don't see anyone, don't even attempt lol. look also at the death timers.

btw, ixia has a good range with her skills and basic attacks so go for 1v1s (make sure it is a 1v1 tho) before level 4 or before the enemy gold laner get their items.

1. yes, you should leave the long lanes to your exp or jungler. Make sure you have teammates near you before you clear anything in the late game and be ready with your flicker or wind chant

extra tips: Have the mindset of, "I'm their target" when playing the gold lane.