Pilot16 I go along with
Genghis on this topic.
Any bag you have already got, will do at first.
After a few more flights, you will work out exactly what suits you, & the partcular collection of items (or rubbish in my case
) that you want to take in the aircraft.
Bags/cases from the specialist pilot shops may suit you, but can be expensive. Personally I have bought very nice ones, cheaply, in my local market. At present my favourites, are a large bag with umpteem divisions & zipped pockets (about £15 from Costco) & a smaller similar one, that came FREE with 10 boxes of photocopier paper!