Tough question. and I do agree don't skimp on anything but if money was no object you wouldn't be asking for options.
So tools that speed your production pay for them selves over time. I'd heed the advice to the chisels above. I'm a machine stitcher but I'm now getting back into hand stitching as it just looks better on some things and in some joints it's unavoidable.
You don't need an expensive hammer. a good Ball Peen will do. a nylon mallet will work as well. Cutting tools that can be resharpened are worth the money. Learn how to sharpen and strop your blades. Good edge tools are going to be a must for boutique wallets and hand bags.
Now here's one thing few talk about. The quality and hand of the leather you buy. Do not cheep out on the leather unless you love frustration. At a minimum for a high end product you should be buying Herman oak, for Veg tan. I highly recommend Wicket and Craig for bridle leather and also if you can find it in this country is Sedgewick English Bridle. this makes great belts and straps and nothing compares.
Thin English bridle make beautiful wallets and cases. it's very easy to work with and cuts exceptionally well.
Tandy is not the place to go even though they recently began selling Herman oak leather. it's online only and the local shops don't carry it or they don't advertise that they have it.
Remember. when a person buys a bespoke top quality product. they expect top quality. from the glue, thread, leather and finish. it all must be top quality not to mention your skill and labor.