Leathercraft seems to be more of a solitary hobby and not so much an apprentice hobby. I am a beginner as well and just started by getting a $6 book on amazon and using old pieces of clothing leather - belts, shoes, purses - to practice stamping, cutting and punching. I don't even have any real tools yet, just things around the house. I was warned not to buy lots of stuff until I actually run into a design problem that a specific tool would solve....like cutting a super straight line without waves or frayed edges.
Your bag looks like the first bag I made. It has the earmarks of being made by someone who has experience sewing fabric and apparel. Fabric sewing and leather craft have many shared skills, but leather has stand alone skills that you will need to learn. Many crafters here have learned through on-line tutorials. I started with this book, which I would recommend. https://www.amazon.com/Leatherworking-Handbook-Illustrated-Sourcebook-Techniques/dp/1844034747. This book is also a wonderful resource for bag designers https://www.amazon.com/gp/product/9887710806/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
My general rule of thumb is that the combined width of the braiding strips should about equal, or be just a touch over, the circumference of whatever I'm braiding around.
How many thongs you use depends on the style of braiding you're using. You don't mention what you're making, but along with u/Puzzled_Tinkerer recommendation, I also like this book for braiding advice.
If you can find a cheap copy of Handmade Shoes for Men by Vass it would give you an overview. The only reason I don't recommend it highly is because it is thin on technical information. It does have good pictures of the process though.
https://www.amazon.com/Handmade-Shoes-Men-L%C3%A1szl%C3%B3-Vass/dp/3848003686
So, I think back when I started (almost ten years ago? Damn, I feel old now...) I found my original instructions on leatherworker.net. I don't have it saved, but it might still be there somewhere. But here's my basic steps, and some tips.
:P Hope this helps? I tend to talk a lot about what I make.
I got this Idiot's Guide book and it was pretty helpful as far as basic info goes. Plus it has some nice patterns.
That is a great series of book. Same with Valerie Michaels. I guess I am looking more for a dictionary of bags photos.
Looking for a book with just pictures of common styles of bags and briefcases, gussets, enclosures, ect. Almost like there are 100 different styles of dress shoe, men and women, and maybe 20 common ones, like oxford, wing tips ect. Much like this book, but for examples of bags..
Amending that ... Snake whip - Link - like that way more ... will say though, you can add length to the whip with several of the tricks outlined in here ... Ron Edwards Whipmaking 2nd Edition.
Basically, if you are short, back track a few passes and splice the ends together or in case of paracord - just fuse them and then resume braiding.
I recommend picking up a copy of Deerskins into Buckskins by Matt Richards. It it is a good comprehensive intro to hide tanning.
I'm pretty sure it's this one...but I'm ordering soon...so don't own it yet. I left the book that recommended it in my car today...have to remember to bring it in to page through...
http://www.amazon.com/Braiding-Fine-Leather-Techniques-Australian/dp/0870335448
If I get a deer, you can have the hide. Also, check out this book. I found it very interesting! I plan to learn to tan one day but the process is so involved, I would have to freeze the hide. I have no time for tanning after hunting because I'm busy butchering for a couple weeks.
Deerskins to Buckskins is the tanner's bible. It not only describes to process to tan a hide, but explains why, which methods work and which don't. I'd recommend it highly.