Parasite should begin with a single rank of infest, some mana potions, and the components for an early blood chalice in order to make his way through neutral camps efficiently. Always start by infesting the most powerful creep in a camp, since you'll also get the gold and experience for the unit you're inhabiting. Depending on your preference, you should either stick with a single rank of infest, and prioritize leveling Leech and Draining Venom, or maximize your damage and movespeed while inside creeps by training Leech and Infest to max at the start. Facehug should be trained whenever available, as it provides an extra spurt of mobility and burst damage. Keep in mind that items, while valuable on any hero, are not a prime necessity in order to perform well with parasite in the early-mid game phase. You should roam and gank with your allies whenever possible, and focus on gaining a level advantage. As an intelligence hero that gains bonus damage to all sources with his passive, Parasite can gain up to 24% bonus damage when using items such as codex--making it a viable pickup for boosting his damage output. Other great items on him include puzzlebox, stormspirit, hellflower, and, depending on your preference, either ghost marchers or steamboots.