LOL in the bot lane...

This is just a general idea of the bottom lane.
DON'T GET MAD AT IT

The bottom lane of league of legends, LOL, are generally made up of the
                             Attack Damage Carry    (ADC)
                                             and the
                             Support                           (SUP)

 The general goal for this lane is to get the ADC to farm of minions and kill the enemies which initiates the point of being "FED."








THE OBVIOUS 
The support sets up the kill getting an assist and keeps their ADC alive.
The ADC, is generally a marksman, or ranged champion that scales better of Attack Damage (AD) than Ability Power (AP).
Each role has different sets of champions that can play them...
The ADC should be the only one to last hit a minion, the support should just auto attack minions before hand, to set up minion kill for ADC or if the support has Relic Shield (item)
Same applies to enemy Champions Kills... Let the ADC kill the enemy, support set up the kill.
You do get gold for the assist...
To get an assist you have had to dealt damage in the same sequence the kill happened.

Ways to support...
The Displacements, a.k.a grabs or pushes and most importantly stuns
Examples of champions: Blitzcrank, Thresh, Alistar, Morgana, Lux, etc...

The Second Tank, I say second because generally top lane is the tank bruiser most of the time...
                     TANK = take damage in place of ADC,enabling the least amount of damage to  ADC      when engaging and or escaping
Examples of Champions: Blitzcrank, Alistar, Taric, Leona

The Pokers, using spells to hit enemies to either push enemy away or setup an easy kill
Generally every support can do this but it is easier for certain champions
Examples of Champions: Morgana, Annies, Zilean

The Healers, Healers give their ADC, health and mana when needed
Examples of Champions: Soraka, Sona, Taric,
Some only give health, so know who does what....

Ways to ADC...
The Pokers, using auto attacks or spells to hit enemies to push enemy away or setup and easy kill
Generally any champion can be a poker, these are just ones I like to poke with
Examples of Champions: Caitlyn, Tristana, Lucian and Varus

Most pokers, due to their spells, are played more passively than others, Caitlyn is one I play passively with because her abilities and kill potential are heavy reliant on auto attacks.

Bursty, have the spells to throw them all out to do extra damage on top of Auto attacks
Bursty Champions, I generally play aggressive with and am patient against.
Examples of Champions: Tristana, Vayne, Lucian.

Who to play...
Well I can't tell you that...
What I can tell you is consider this type of player you want to be,
Do you want to be aggressive and have high kill potential? Do you want to play passive and have a late kill potential?
Play a champion when the come out for free of the week, see how you like them... Do you love that champion? Then play until you can get him and main that champ