Mostly - CS better. You're winning your lane via kills but losing any advantage you gain via CS. e.g. yesterday (Ezreal v Vayne) you had 135cs to 241cs for Vayne (and Ezreal has a significant advantage in that laning phase). The game before that you won against Caitlyn and were down 134CS to 218CS.
You're getting a 50-50 because that 80-100CS difference is worth 4-7 kills, which means your 3-7 kills advantage is negated by your CS disadvantage in a lot of games.
Secondly, ward more (and in better places, likely). As a support secondary you should know better. Even with bronze 4-5 allies, you're often the least wards placed on your team. 6 or 7 wards placed in a full game (when you always have yellow trinket and never swap it out) is pretty unacceptable. I think this paints a pretty clear picture:
http://wardscore.loltools.net/?name=ouioui2012®ion=na
In contrast, here's mine (and I'm not a pro-warder by any means - I'm low gold):
http://wardscore.loltools.net/?name=valyrianblade®ion=na
I outward you in support despite being autofilled there and frankly being dead too much to get wards out (I'm an awful support).
In bronze (admittedly I've never been there but I'm guessing) vision is one area where you can single handedly make a HUGE difference for your team. Your allies won't notice it, you won't be credited for it, but it will win you games and you will climb because of it. In low elo play where ever fight is a messy skirmish (aside from 5 on 5 death brawls mid lane when it gets super late) having vision in the jungle to be the ones with the factor of "surprise advantage" is huge. Your fed ally who insists on split pushing will have vision to see people incoming, and your remaining teammates can also see them heading for him and take something elsewhere. You'll also catch the enemy jungler/support wandering in to your jungle and get a kill or two, which in low elo often turns in to 4 or 5 kills as each enemy runs at you one at a time trying to save his ally (as that person dies). It's the freest of free wins - low elo players always try to save their over-extended allies and in doing so over extend themselves.
Otherwise, there's the other standard stuff. Objectives win games, not kills. Not even Barons or Dragons to be honest (I mean, you want those yes, but turrets are arguably more important at your elo). Now please don't go tell people a gold player told you turret is worth more than Baron so the Baron call is wrong, blah blah blah. Baron is way better than pretty much anything other than end game / double nexus towers / triple inhibs (possibly similar to double inhibs). What I'm trying to tell YOU though is that at low elo I'd imagine most players are awful at USING Baron properly. Baron is WORTHLESS if you don't take any towers with it. So basically, Baron is only worth as many towers as you can take with it, which means if your team can't be trusted to use baron to take at least 2 towers, you're better off taking 1 or 2 towers on the play rather than going for Baron. To win this game you NEED to kill at least all the towers (plus an inhibitor) in one lane - that always needs to be your priority, every time you have an advantage you should be asking yourself "how can I take a tower off of this advantage".
As for more specific advice:
If you win bot lane, you should take bot turret ASAP then rotate mid. This is bronze so your mid laner probably won't like it / won't understand why it's the right move - so tell him that he's better at getting kills than you and will get more fed in the lane where they don't have a tower (when really the reason is you're a tower-taking machine and thus need to be in a lane with a tower to take!). Of course he doesn't need to rotate bot, if you rotate mid effectively (should be easy in bronze with the enemy's warding and map awareness) you can get a kill on their mid laner with your 2 man gank, and then take the tower before he comes back. Either way, once you get mid tower then continue to rotate to top lane. Works best when you literally take bot tower, go mid and get kill + mid tower, go top and get possible kill + top tower (all without recalling). Just push the momentum, and taking those 3 towers without the enemy getting 1 in response (or possibly just getting bot, but more likely they'll try to rotate mid after you but too late) gives your whole team a massive lead in gold and map pressure that is incredibly hard for the enemy to recover from. The biggest part of this is that those 3 towers are all global gold - meaning that your allies who aren't getting ahead themselves are now ahead (and can help carry) and the ones behind/feeding are now even (and can stop feeding). You want to be the team to initiate grouping as in low elo people don't notice early enough and won't back off and will give a kill and an easy tower. At least, that's what worked for me when I mained ADC in past seasons and I used this to climb out of silver each time. Whenever I had an edge in lane go for first tower, then go for the other two lane's outer towers. Works way better than trying to just snowball in your lane. The problem with staying bot lane as ADC once you're winning lane is the enemy team knows where you are and they know you're strong. You're putting a huge target on your back for a 3-4 man gank which can turn in to bot tower + dragon for them. It's not worth it, don't stay there. Get the tower, then get out and you group first and do the 3-4 man gank on the other lanes.
