Ok. Seems like you need to learn how to obtain freelo.
Get champs like Garen and warwick(don't judge) and Darius.
Next, make sure that the enemy hasn't counter picked the champ you want.
Finally, wreck them like a scrub because these champs are simply so broken.
And remember, ALWAYS BAN TEEMO!!!(he is main counter)
As for actual advice, you should try freezing. Don't really push too hard unless they are playing an farm based champ (like gangplank). Just try last hitting minions, and only last hit minions. Unless they are pushing extremely hard, which in that case, they are overextending, which allows your jungles to set up easy ganks to obtain free kills. don't really try to push unless they are like gangplank(as stated before), but make trading all depends on your champion and theirs. If you have a champ that is good for trading against their champion (Garen vs riven) then go for it. If you are not, (Garen vs teemo), then just far under tower. It really depends on. The champions in play.
If you need for detailed help, just reply with more detailed information, like who you usually play as.
Note: take my advice with a grain of salt, as I am level 27, but have a good knowledge.