The key to flash is knowing your environment as a killer you need to know your prey and this kit helps your durability to lane and when the right time comes to strike. power pen helps a well timed ult to swing a fight and the slow and health can really help your team hunt down an opponent. if your opponents have strong attack build up the helment otherwise tier 1 is fine . If they are power strong like star or green lantern supepmans suite is a good defense because of the will and health or for early game mirrors can help . Starheart is a must to max YourQ damage and add extra punch to your W.  Starheart mixed with cosmic belt makes your ult very dangerous . Add the Books pen to your set and your a deadly force . Stolen powers teleport helps with leaning and helping team and cars do work on champions put is more for clearing drowns . Will regain is very important for his passive and to be able to always be in attack mode. Overall flash can play many roles on a team and is fun to play