At 1433 elo here, but I got a few tips:
A Couple ad junglers that are simply amazing are nocturne and tryndamere. If their ults are well-timed in a team fight, you can reap huge benefits. At the lower brackets, support is definitely not necessary. In 1400 elo you need support because the other team will always have a support. A lot of times if I am doing well -- doesn't matter if I am an ap carry, tank, jungler, whatever - I will probably buy 8-10 wards over the course of the game. When you think about it, 750 gold is a very small price to pay, especially if that means winning 2 teamfights. (4 kills per teamfight) x (2) x (400-500 gold for your team per kill) = 4000 gold. Obviously, paying 750 gold for 4000 gold is a great deal.
You have to consider the team's overall benefit before your own benefit. Small things such as always buying a ward on your first trip back (yes, even if that means you can't complete an item) are huge. For instance, do I get merc treads, or just null mantle and boots and a ward? A ward saves you from dying or potentially allows for a kill, for only 75 gold. If I mid, I have at least 1 ward covering top or bottom of my lane at all times. It gives huge map advantage knowing when the other team is trying to gank and what not.
Summary of huge wall of text:
-Buy wards, lots of them
-Nocturne, Tryn, and possibly Xin for jungling (really depends on what suits your playstyle)
-Morgana, Annie, Brand for ap carries
-Focus on overall benefit of team before personal benefit (i.e. warding baron/dragon if you have the extra money or buying 2-3 pink wards if the other team has a bunch of stealthers)