Support item components are boring compared to other classes.
: Bonus damage on your next spell after killing anything. Creates an interesting window of power to help you win trades if you play around it
: 20% max mana restored on level up. creates spikes in sustain to play around near level thresholds. When your mana is high you're encouraged to burn spells right before you level up. It also grants less power if you're being overly safe and not burning enough mana to be below 80%
: Great against aggressive enemies, not so great against passive enemies. The more the enemy is fighting you, the more you can fight them or push the wave without being drained of your mana
: An active slow. Not much needs to be said. There are very few active components.
: Helps you passively push the wave to conserve your mana and cooldowns, but you have to position further up to get the most of it
: Empowered autos after every spell rewards weaving spells in between autos
: Empowered autos every 40 seconds. #WindowsofPower
: Movement Speed around turrets, makes your champion significantly more mobile around them
and 
: gains stats for CSing, starts out weak and scales up to be stronger
: AoE waveclear attached to your autos and a Psuedo reset
: Reward's extended fights over shorter ones
Meanwhile almost every single component for support items can be summed up with two words: "some stats". They don't do anything interesting and don't really change how your character plays in any significant regard.
now there is a lot of items you would think is not for supporting but that shows you, you don't know what you are taking about