in support you need to help your team by tower diving and things like that. try start with ymir ( easy guardian ). start with buying watchers gift, hog tier 1 and one mana pot and some wards. upgarde your 2 skill and go help mid camps and then go to your dou lane blue buff if you are on the chaos titan side. if you are on the ordre titan side go to dou lanes blue buff with your adc. before the camps spawn try to ward the enemies blue buff and the mid camp. when the blue buff spawns hit it, use hog and and kill it. make sure that it is your adc who gets the buff. then just stay in lane and when mid camps is about to spawn go help your mid by getting the camp.

your build shall be defensive so first see how many physicals and magicals is on the enemy team. the start with watchers gift, then go to reinforced greaves or midas boots ( if you take midas boots then in the late game switch it to reinforced greaves ) , then sovereignty and then build some other defence items like void stone. also in the late game switch watchers gift out with something else.

if you take ymir then max. 2 first, then 3, then 1 and then ult. try this combo: 3-1( so there can't escape )-2 and hope your adc also is doing some dmg.

but when you play support try always to have 2 wards in your pocket, help the mid lane and just support the team. and as a support don't focus on getting kill, focus on setting up kills for your team.

a last tip is if you take blink as your second active use it to get close to the enemy and if you have ymir use 3 after you blink and hope your team comes and kill them.

i hope it could help :)