I found the account of a shopping trip absolutely riveting, especially as I have done a fair bit of dressmaking myself.

I think the "bugle trimming" is probably bugle beads already attached to lengths of ribbon or strips of gauze. If JA had just bought the beads I think she would have said so. Also, attaching beads is very fiddly work, so if a dressmaker is going to be paid to make up a garment it would almost certainly be cheaper to buy the trimming ready-made than to pay her to do the beading from scratch.