I main 
and have about 900 games on him. I am usually playing passive, freezing the lane and just farming easy. But I always hear from people that the agro player wins most the time. So how do I play agro? I try pushing tower to their lane and harassing the enemy, but I just get ganked and killed because im limited to 1 ward. So I either ward the river or tri brush.
So how do I do this effectively?
You main Jayce and you play passive in lane? How do you win games? Combo the enemy laner 1 time while trying to lose as little hp as possible. After that just walk up to the minions (provided the enemy laner is melee and can't withstand your burst) and prevent them from farming. Freezing the lane is pretty helpful so you are't getting ganked over and over. If the enemy laner gets close just all in and if they aren't dead that probably will have to recall. If you aren't farming you should be damaging the enemy laner.
My best advice is to invest in control wards. Keep one on your side, use your trinket on the enemy side. See if your jungler can get scuttle, as well. Vision makes a ton of difference.
900 games on a single champion and you haven't started to get a sense of when you can all-in someone? Or how to trade?
This is what you do: Find a tank top laner, load him with nothing but defensive runes and masteries, and play him aggro early. At least then you wont be punished as hard and can learn something about trading.
Additionally, I just read a post below about your map awareness and wanted to say you need to go to a website that has a free online stop watch, set it to go off every 10 seconds, and leave it running while you play league to remind you to look at your minimap. Once you get used to 10 seconds, reduce it lower. Rinse and repeat until you do it without thinking at regular enough intervals where you can react to the vision your wards give you.
Number 1 mistake I see Jayce players make in laning is sitting back in cannon mode all the time and saving hammer stance for trades. Ideally you should do that the other way around and here's why: Hammer stance W gives you mana on hit, and Jayce is mana gated. So if you do your CSing in hammer stance, you just recovered a good spell worth of mana per wave for free on top of regular mana regen. Moreover, the trading pattern starting from Hammer stance is safer: You jump on them w/ Q (AA at least once) and maybe use W for added dmg, then punt them back w/ E and then switch to cannon stance and add more damage to your trade, and from range now, so you are free to decide when to end the trade, and there's much less your opponent can do to try and re-engage it+they just took a ton of damage aren't likely to want to resume fighting anyways.
The suggestions of MrFawknSunshine below are well worth taking advantage of to deal w/ the threat of jungle ganks. Moreover, if the enemy top laner is chunked out hard, you can sometimes turn the jungle gank into a free kill or even a double. (Also, it's not a bad thing if the enemy jungle is camping you, if you're drawing that much attention to your lane, then your teammates have the opportunity to make winning plays elsewhere on the map, like in bot lane). You might wanna try jungling for a few dozen games to get a sense for what the role is like, to help you understand what to expect from the enemy jungler.
Not sure if this vid covers what you're looking for but it's got 20 straight minutes of laughs and Jayce tactics you might find useful.
