Typically a good blend of all essential amino acids in free form may be the best.of course it is always best to take both essential and non essential combination. You can also alternate with whey protein, but make sure it has all the amino acid combo.

There are 11 amino acids considered essential (your body cannot make these so needs them from food) and from these essential your body will be able to produce all others (like glutamine).
However the free form EAAs are to help the body make its own enzymes (amino acids are needed for this) and to strengthen digestion in general so that it can digest the protein (from food) and get more AAs.

Free form aminoacids can be absorbed quickly and immediately put to use and start healing the gut wall. Bear in mind that if your digestive system is fragile it may mean that other parts of the body may be starving for the right nutrition as well so your body will use the nutrition, like AAs, based on priorities.

Plenty of free form amino acids, efas, nutrients and other easily absorbed nutrition can work great. Glutamine is traditionally used to heal gut wall (non essential amino acid), but primarily supplying the essential aminoacids may allow the body to convert to whatever other AAs it needs.