How to play Rek'Sai

First, you want some assassin masteries and runes, attack speed is needed. Then you start gromp or blue on blue side cus u need the blue buff don't ask me why. Another option is to solo or duo/triple invade the enemy krugs and go back to blue side. Most people start red or krugs and that is fine but if u start blue u have less chance of being invaded or getting blue stolen also u need cdr. Now for the jungling item, since reksai was nerfed so bad and therefore no longer has the great sustain she was known for early on, u are gonna want scavengers smite, also a lot of people say go cinderhulk reksai is a tank or warrior cus she is a warrior, but if you have played reksai when she came out then you know her first reccomended item was devourer. So you are gonna want to grab that, get devourer cus u want attack speed, it goes with ur q which is a good source of dmg and fury. Then after that u are gona want to get hydra for some burst and then bork and something with on hit effects like shiv so u can make use of the stated devourer. Then u want a few tankies so u aren't such a glass cannon like randuens or spirit visage after u get some life steal. Like I said before about the life steal thing, get some life steal like a lot like get BloodThirster cus then u can heal when u attack stuff and what is better than that? Also since u are a burrowing creature and still get blocked by minions get PD(phantom dancer) so that u can be more realistic

A full build may look like this Optional ->

Now for the gameplay

Rek'Sai is extremely squishy early game, and mid game... and late game, so you are gona want to have no fear when in skirmishes and just dish out dmg and u will die but u need those deaths for the late game. Also a lot of champions in league of legends say don't hesitate or u will die so I would listen to them. Another thing, Reksai is a burrowing creature, Ive said this before but it needs to get in ur head, that means she likes to be underground a lot so be burrowed as much as possible, but be careful cus it limits ur vision of non moving units and is slow at tracking moving units. When ganking use ur q to give away ur position, it might scare them off and get a flash, but if they don't move or start attacking you just go in for it, remember I said have no fear, anyways go in with your e in ur underground form and knockthem up, this is a useless knockup since ur unburrow animation is basically almost longer than the knockup so this is just for asthetics, now just q a lot and e at max fury for true dmg that isnt very good but it is dmg. After that u got urself a triple cus the enemy eilse tried to fight u too and elise, well we know elise.

Hope this helps and remember, sometimes there are just bad games