Man, Smough & Ornstein on the first playthrough is a pain in the ass. I still have nightmares on that fight… But just 'cause I didn't know what to do. Anyway, some tips:

- Ornstein is vulnerable on Fire, while Smough on Lightning: bring some Pyromancies and the Lightning Spear from Sen's Fortress, upgrade it at the Giant Blacksmith and that should be more than enough (ofc you need decent VIT and maybe the Eagle Shield which gives +80 def against Lightning);

- Stay behind the pillars at all costs when you need to heal: also, iirc there's still a possibility to stuck one of the two guys at the column, which gives you extra time to heal/dodge/recover from staggering;

- One final word: go in human form, because in the big room before the boss fight there's Solaire summoning sign. He'll give a big hand on them, especially during the first phase. Consider him your 'meat shield' .