Just a bit feedback (plants,items,adc)

Plants: I think they are ok. They have enough impact on the game. Not too much and not too little impact. Also it gives the jungle more of a feeling of a jungle -> more type of plants could be good to stregthen this feeling -> but you need to take care of the balance then. My suggestion is that meele only need one and ranged need two autoattacks to use the plants.

Items: I think there are too few items. There should be more items to help you in specific situations, against enemies or the items of them, to strengthen the strengths of your champion or to strengthen the tactics of your team. For example: If I play any mage at midlane, then I have literally only abyssal as a offensive and defensive option against another mage and only zhonyas against ad champs. I don´t have any other options which I can build to still deal some damage but also defend me from his damage. But more items also means the game will be harder to balance.

(Just my thoughts and ideas about ADC, don´t take that part to seriously cause I know that it has many flaws) ADC: I think that there is a problem with the ways you could build your adc. The three possible ways: Crit; Armor penetration; On-hit (only good even if it is op on a few champions). Most of the time either armor penetration or crit is overpowered. With the rework of armor penetration I think crit will be the best option next season. But it shouldn´t be: What is at the moment op? It should be: Which option is better? And I think that also crit could need a rework so that armor penetration and crit builds feel more different from each other and both have other purposes.

Crit: Should have the feel of really powerful autoattacks, which also means that those autoattacks would slowly be prepared. For example: A channeling time for crits (except crits through abilities like Fiora´s E). The channeling could be reduced through levels or attackspeed (but with a cap of the reduction). While the champion channels the crit, he has a movement speed boost. Right after the first crit (this mechanic would be set on cooldown if you are out of combat) you can do the next autoattack or channel the next crit. Also there should be more items than randuin to reduce crit damage (with a cap of 20-30% reduction). Reducing the attackspeed of crit items and buff the ad or crit chance of them. The purpose of crit should be to burst squishy champions while you have a harder time against tanks or bruisers which build armor.

Armor pen.: Should have the feel of doing frequent damage to enemies. For example: Increasing the attackspeed cap to 3.00 from 2.50. Adding items which give lethality and attackspeed or attackspeed and attackdamage (making sure by adding lethality items that those won´t be abused from assassines). The purpose of armor pen. should be to deal frequently a constant amount of damage. It should be better against tanks.

(Let the downvotes begin xD)