So i just got the ability to upgrade my stuff, but I feel like I'm not getting something. How do you know what helps exp increase (ex. X2) and stuff like that. Any help is appreciated. Does it explain more as I keep playing on?

It doesn't explain anything, organic stuff gives the mulitplier and tech stuff gives more xp and eats up the militplier. buy 99 coloured jellies and 36 of them on your weapon gives it x3, the highest you can get, then buy a bunch of super conductors and add a bunch of them to get the most bang for your buck. You'll have a fully leveled up weapon in no time, also you can evolve your weapons once they reach their max level and just do the process over again.

" @The_Laughing_Man:   Thanks for the link. So it seems like I shouldn't upgrade until chapter 10? "

" @The_Laughing_Man:   So should I wait? "

 http://ff-13.info/category/weapons/
 
just look at how much xp weapons need to get to next level, then toss 36 vibrant oozes to get 3x multiplier, then toss in perfect conductors till you get enough xp to max out a tier