like what paragim (or however you spell it ) shift should i keep my characters in, 
 
 what summons should i  use ,  
 
what level should i be at for the final boss?

They do a nice job wile setting up the battle system. Just read the info and you will be fine. Also there are no "Levels" Just read the info before you rush in and you will do fine. 

You don't need advice. The game treats you like a newborn for the first 20 hours.

Always keep a medic on difficult fights.  On normal fights just have RAV/COM/RAV to stagger, then switch to COM/COM/RAV to finish the fight.
 
Also, sell your credit, incentive, or premium chips.  DO NOT use them to upgrade your shit.

the game gets quite hard in the last chapters... in fact, i went from really wanting resonance of fate to...well, not wanting it, because FF13 is wearing me out to be honest, i just want it to end now, and it seems fate is hard from the start >_> I need something to relax next, like Sonic All Stars Racing!

Whenever you get a chance, farm CP. A couple of the bosses can be hard as hell. One in particular is Daharka. Don't worry about Mark missions or upgrading your weapons all the way until after you beat the game.

" They do a nice job wile setting up the battle system.

" You don't need advice. The game treats you like a newborn for the first 20 hours. "

You know how Buffs and Debuffs are usually useless in most RPGs?
 
Not this one, spam them constantly.

Don't sell your accessories. There are a couple of them that you can only find once or twice and if you sell them you won't get that award.

Don't keep your characters in any one paradigm.  In fact every other turn you should switch paradigms, even if you are switching from one paradigm to another identical to it.  This is because every other turn you get a full ATB when you shift (so you start in one paradigm, issue one full round of commands, then shift.  Then use your free attacks and one more ATB bar worth, and then shift again).  ALWAYS SHIFT.  You're slowing yourself down otherwise.  My 'default' paradigm though is Com/Rav/Sab (Fang/Light/Vanille respectively).
 
Don't waste time by always having a Medic or Sentinel.  Switch to those when you need them, and switch out as soon as you can.  If you want to 5 star fights, you need to be spending as much time being offensive as you can, typically.  It may seem like a good idea to have Sen/Med/Com or Com/Rav/Med but you're wasting time using those unless you need the healing right then.   
 
Saboteurs are your friends, every enemy can be debuffed.  Even most bosses are vulnerable to a few debuffs, and they make an immense difference.  Especially debuffs like Deprotect and Deshell.  

" You know how Buffs and Debuffs are usually useless in most RPGs?  Not this one, spam them constantly. "

" Don't sell your accessories. There are a couple of them that you can only find once or twice and if you sell them you won't get that award. "