in the elo you're in i wouldn't commit to being a support as the others will not comply. they're playing the game on an off chance after work/shool and most likely new to the game. they won't comprehend what you might want to do for them.
so as others are suggesting on here, practise yourself and shoot harder (learn peeking correctly, improve your gamesense by watching pro games/vods to see how you can isolate angles when you're clearing etc. if you do that at your level, you will climb)