a lot of the things i write are on the piano,which i happy with, it totally works for a piano sound. but a lot of the stuff i listen too they have these cool synth pad type sounds. and just diffrent things they put into the mix that all sound good to me. i'm just curious how would you start to build your own sound library or where would go about finding these things.
The answer is ofcause: the NET!
However !
You must make sure that the files you find are either licenced as MIT or CC0, because then you can use them freely in your derivative work!
But if you take care of that (and scan for vira), then there are mio'S ..approaching ..bio.. :! of samples online.
That said, why limit your self to samples?
Get a VST! I recommend you to get Synth1
Installation is needed, but then you have the most versatile and exciting soft-synth, that has the biggest supporting number of FREE banks.
Aside From that, you can look at other VSTs too, but every time you test one, then ask yourself
"Is this better of different, than Synth1"?
If it is, then perhaps get it, if not forget it!
Learn about using VSTs here: https://lmms.io/wiki/index.php?title=Working_with_VSTs