Lower skill player, decent understanding: Seeking help to become better team player

Hello! I came upon this site, and would like to ask for some help in game. Thanks in advance for reading.

I've played about 50 hours of the game so far, and I have been proud of a few performances. However, I know my place, and it's toward the bottom of the skill curve. I've only played Single Draft so far, since there seems to be less pressure than All Pick. As for specific things I would like to learn, there are a few. I feel like my last hitting and denying is slightly above most of who I play against, but that obviously depends on hero choice. I think I am weakest in item/skill builds, and using my abilities in the best and most efficient ways. I would really like to learn how to best help my teammates in laning situations and teamfights.

On the topic of what role I feel comfortable in, I would probably put support at number 1. According to the game client my most successful hero is Witch Doctor, but that's mostly because I've drafted him more than others. Either way, I do enjoy the hero, and I understand his abilities. I tend to have trouble hitting Maledict, though.

If anyone is willing to lend advice, or even wants to play a game, it is all greatly appreciated. I can be found on Steam as DJRolling. I live in the eastern US, match make for that region, and usually have time to play between 8pm and midnight EST.

Thanks again!