Toxic cloud isnt really worth it, easy to avoid. If you want to blow people up combustion is lol
for stats you should look for something roughly around this (I dunno if you plan to pvp or what not but)
40 end because you stop getting stamina after 40
40 vit or so is usually a decent number to stop at
str/dex weapon min or pump up whichever one if you want to stat scale
16 attune is good for pvp, higher if you want for pve maybe?
int depending on build either high or not, depends on what spells you want
faith same as int
Right now i have a dex build and a Int build, so far I'm liking my int build better since pyromancy blows up melee and my sword uses int scaling anyway. End lets me use heavier armor and not move like a turtle + havel ring
Keep in mind that if you invade they can use flasks to heal while you can't. However you can pop humanity, twin humanity or divine blessings to heal if you want. Having people popping flasks can be really annoying the best punish if usually a backstab or if you have a really powerful spell like crystal soul spear that is good.
I love me some Dark Souls pvp