the function of the starter is to have a shingle under the gaps between
the shingles of the first couse. i have seen people cut the bottom
portion of a timberline shingle off, and use the top portion for a
starter. you can also get actual starter strip that goes with
timberlines. when i put shingles on my shed, i just cut a shingle into
small pieces and put one under each joint in the first course (wouldn't
do this on a house, but on my own shed it was fine).

you can nail the starter fairly close to the edge of the roof to
prevent the wind from picking it up. then, the first course of
shingles will glue themselves to it.