Unranked support main (Soraka, Sona, Leona) here. I took a glance at your match history to see if I could pick out anything that you could really improve on. The first thing I noticed was that you never upgrade your trinkets, which significantly weakens your vision control. You seem to be warding reasonably often, but the ability to sweep wards out of a broad area rather than a single bush should not be undervalued. The second thing I noticed was that you almost exclusively play Janna. Janna is a fine support, but her particular specialty is disengage, which is not particularly useful at low levels of play, where many people focus almost exclusively on getting kills and diving into risky or unnecessary fights. Janna is excellent if your allies appreciate caution or even calculated risk, but you may want to pick up a couple other champs who better fit the play style you see around you and apply them to the team comps you see forming. Of course, this support main has never even played Janna, so take this advice with a grain of salt. I'm still working on rounding out a support roster to properly benefit from draft picking, and I imagine you can benefit from it as well.
Areas most people can improve on: Lowering death count, focusing on objectives, communication, friendliness, asking others to help ward.
Many players in the lower ranks focus very hard on killing their enemies as often as possible, which leads to a lot of aggression and a lot of unnecessary death. For yourself, focus on keeping your death count as low as possible. If an ally is chasing into the fog of war and you don't know where the enemy bot laners are, ping them out and don't follow them in. Despite what everyone says, the job of the support is not to save their carries but merely to make it harder for them to kill themselves. There is no sense giving up two deaths rather than one and giving your opponents free reign of the map while you sit in base and lose gold and experience. My play improved significantly when I started focusing on keeping myself alive, and I imagine you will get the same benefit. Treasure caution and punish over-zealous opponents.
As stated in the previous paragraphs, many low level players focus on killing enemy champions over anything else. Your time will be better spent focusing on objective capture and wave management than on getting kills, especially as a support. If you get an advantage, as by winning a fight, ward out the area in which you have gained control and push it until your enemies start moving against you. Capturing a turret or dragon in this way will help your team more than roaming mid for a gank or invading the enemy jungle. If you plan on making a coordinated push down mid, set up large waves in the side lanes to push at the same time, so your opponents have to choose between losing side turrets to minions or keeping all five champs for a defense in mid. If your team is wasting too much time on trying to get kills, remind them to focus on quickly challenging objectives whenever the opportunity arises. Even as a support, don't be afraid to split-push or manage waves in the side lanes if none of your allies move to do it.
Communication is especially important at lower levels, when not all players have a good sense of the flow of the game, and as a support player, you are likely to have better map awareness than many of your allies. If you are doing well enough to be credible, coordinate your team to capture objectives, politely encourage your allies to help you ward (having several pinks on the map is amazing), compliment good play, and gently discourage risky or wasteful plays like chasing into the fog of war or uncertain turret diving. So long as you aren't irritating your allies or wasting all of your time typing, increased communication can work wonders. Just be sure to be friendly and supportive to friend and foe alike. Good luck and happy farming!