Here are some of my recommendations. I too am a proponent of good tools. Leather working is one of the few places where occasionally the cheap stuff works better but those are exceptions. First the cheap stuff I recommend:
Tandy stitching groover. I have two of these one set for the two distances I always use.
I use a Tandy adjustable Creaser.
The wooden Strap Cutter that Tandy sells. If you are gonna make belts, or even cut belt loops, slings anything like that this is a must have tool. I had a $300 plow gauge for cutting straps this little $20 deal blows it out of the water. Whoever invented this thing should be sitting on the beach in Cancun drinking margaritas.
After that I'm pretty sold on higher end stuff:
Sewing machines: Cobra 4 for sheath making and Cobra 18 for lighter work including inlay work on sheaths. Some day one of their splitters and a skiver will be in our stables too.
Leather cutting:
A quality roundknife is indispensable for me. Its the one tool that is never put away, it is always on the workbench. I make em and use my own. There are other custom makers out there too and if you are a knife maker ya can make your own, I'll be glad to help but they are different to make. The roundknife/headknife has been used for centuries to cut leather, push cut is the way to go. Many of the more standard roundknives out there are pretty miserable to use. You want thinness of blade stock and edge holding ability.
Skivers:
Many razor blade skivvers out there. Pretty much useless. They seem like a good idea but they just don't pan out. Our own Paul Long (sheathmaker) designed a skivving knife based on what he'd used for over 60 years or so. I built it and it works great. If you are a knife maker be glad to help ya here too or I do sell em. Thinness of stock, flexibility (like a filet knife) and edge holding ability are what a guy is shooting for here. I'm currently working on a prototype of a push skivver. These are European tools and I have one by Blanchard a classic French leather making tool co. Can't say I recommend it cause it just doesn't hold an edge. Many of these classic leather crafting knives just simply don't hold an edge very well. They will get hair splitting, stupid, sharp but after a couple of cuts need touching up. I can do better and am working on it. I use this only in a limited application though and not for sheaths.
Stamping/carving tools:
Barry King. That was easy. There are some other good ones out there but my wife Nichole who does all our flower carving will only use Barry King tools. We have some stamps that are 2 to 3 times as much and they sit in the wood block that holds her tools. BK tools are very well priced too. This is one of those things ya can go crazy on. I've never counted but I bet we have over 200 stamps of different manufacturers. We use the same 10 or so for almost everything. Ya don't need a bunch. BK gets the vote on mauls, mallets etc as well as swivel knives too.
Edgers:
One of your most important tools. We have several from different excellent makers. BK again, Nichole has several from him, I have a turn back edger from Horseshoe Tools I'm very fond of. Honestly, I keep kinda coming back to Osbornes which are a moderately priced edger. I have a #2, #3 and #4 that I use all the time. I have two very specialized ones a #0 and a #1 from a company Mark linked to that starts with a W, that I really like. In the cowboy world many, myself included will not mention that co by name. Shame too because they do make some excellent tools. I can not recommend them due to their business practices.
Well thats pretty much it I guess. If there is something I didn't touch on feel free to ask.
BIGGEST THING:
Use good leather. Wickett and Craig or Herman Oak are the standards. Expensive, yes, worth it, yes.