You have a lot of stuff at your disposal, but not all of it will be time-effective to keep on hand. Depending on what locations you know, and how buff your character is, some may be time-effective for you that wouldn't be for other people. There's:

protection vs. alignment (25%) (works if you're neutral, but the alignment you get protected from is random)
flight
enlarge/reduce
detect invis
stone skin (25%)
aura (20%)
shield (20%)
giant strength
resist {type} (heat/cold/lightning/negative) (33%)
resist mental
misc. hit/dam effects (frenzy/bless/ferocity/etc.)
water breathing
silver/speckled pills
cure blindness
return/teleport potions
haste (much rarer than it used to be, but still exists)
gold

Of those, I would try to keep on hand protection vs. alignment, detect invis, enlarge/reduce, resist {type} (where appropriate), misc hit/dam, water breathing, cure blindness, silver/speckled pills (maybe 4 of each, basically as necro/shaman insurance), return/teleport potions, and about 20 gold. At higher levels, add resist mental. If your build doesn't on bash, and is sufficiently badass that you're not worried about someone bashing you down, you could skip enlarge/reduce.

Stoneskin is available with little effort, but those sources have significant negative side effects. One other source has a minor negative side effect, but a very short duration. The few that don't have side effects require more time and effort to obtain, and are limited. So expect to have them stolen the first time you encounter a thief.

Having the cure blindness, teleport, silver/speckled pills and gold means you can usually survive getting slept by a necro as long as it's possible to flee/teleport. Teleport, cure blindness, then run to a healer using the pills to keep yourself alive and moving.

Also, at higher levels, if you expect to be rotted by a shaman, carry around some non-limited +CON gear in your container.