Here is how you play it, you almost never roll for units unless ur forced to and save all gold til you hit 50. Only time where you level early is the round before krugs to lvl 4 from 5. This is if you have a weak team or are unsure if you are gonna finish the round or not. After that you keep ecoing til you hit 50 gold and from there on you spend the leftover gold from each round on leveling. If you are doing good you will hit 9 and thats where the instawin comes in. This strategy can probably be played with other comps aswell but the warden -summoner strategy has been working wonders for me and have been very effective for keeping you healthy pretty much the whole game. Especially if you hit an early Zyra with Naut and Thresh.