Healing at low levels is difficult if you are trying to be conscious about weight as most items that can be bartered for actual full heals are heavy (armor etc).

Once I hit mid - late thirties I find no issue with this. There are plenty of light items (wands/pills/held items) that can be bartered and gathered in bulk for heals.)

Once you are in outlander prepping is considerably easier due to a skill Outlanders get. What I generally do during the applicant stage is run around higher lv areas that have armor on the ground, and just go around and grab protection/flight potions. Pre lv 30, that should be enough for most fights to at least be in the same league as everyone else.

Flight potions - HTOS/Arial City
Protection - Past/Barovia

Places you can grab some gear

Velkyn
Ruined Keep
Eregion
Azuremain
General dragon Armor
Evermoon