As for Phoenix Downs, you can get several during missions. But the best option, if you are still able to access the Shin-Ra building in story mode, then go to the entrance, and you'll find a woman there that will offer you a free potion. Agree to drink it, because this will fully restore you Hp, Mp, Ap and give you the Reraise status. The only side effect is that your DMW gets reset to normal.If you no longer have access to this, you could always try to buy a few Rebirth Flame materias and do an easy mission and wait until Phoenix shows up and damages enemies while giving you the Reraise status as well