I am wheat intolerant rather than gluten intolerant so I do
some overlap.

Gluten comes from wheat, rye, barley, oats.  Avoid those
ingredients.  This requires knowing what foods are made
from like Bourbon being made from corn (gluten free), rye
and barley mash.

The brute force approach is simple - meat and veggies then
take your time adding other foods by first making sure they
are free of what, rye, barley, oats.  Take your time learning
what contains them and expand slowly.