in ways of armor. As u mentioned the gold hemmed is a very nice set for mid till "end" game when wearing with 1-3 peaces of heavy armor (stone/havels/black steel) but u CANT upgrade it. So as allrdy said above. Have alook at the resistences, pick 1 or 2/3 sets of armor and grind+upgrade those ^^ u maybe look like a guest on a "bad-taste-party" but who cares? ^^ i don't mind to NOT die but look arkward instead of looking cool but getting 1-2shotted by enemys wearing trollface-masks
for 2: i'm nearly the endgame, with a pyrohand+15 but never found a dialouge or soul that says: give/use theez with ***** to upgrade pyrohand+15 to "heavenlypyrohand of the hellsangels guardian bad-ass" ^^ so the magibonus of 250(i think it is) with a scaling of S in int and letting u 1-shot most enemys (it took me 3-5 chaosballs to almost kill ornstein with a pyro+15 and 20int) seems more then enough, if u keep in mind u can go waaaaaaaaay past 20int and a S scaling.
for 3: i thought it u get +1flask if someone kindles a fire u kindlet before, but might be wrong. Only playn' for a week now and most things in Dark Souls confuse me....like fogringcasters and Chanbackstabbers
Hoping this might help u so far ^^