My recommendation for starting leather craft is VEGETABLE TANNED COW LEATHER.
There are many varieties when choosing the leather for your project.
Depending on the purpose and craft nature different types might come in handy, however the best suited leather I find for my craft/carving, and for you is Veg tanned cow leather.
VEG TAN? CHROME TAN?
Tanning process makes Raw hide into a craft friendly and tool-able leather.
Vegetable tanning is a long process using Vegetable oil (Tannin) and it can take months, but ends in higher quality leather. Veg tanning will produce Firm and Thick leather making is suitable for carving and hand crafting.
Chrome tanning is a lot quicker process using chemicals (Chromium). Chrome tanned leather is relatively thin and stretchy and therefore I do not particularly recommend for leather crafting.
I only use high quality veg-tanned leather.
Thickness will be something you personally should consider for your project.
I usually use 2mm for carving, or for outside layer of wallets,and use 1mm leather for inside and pockets.
It all depends on what you want to make and how you wan the end produt to be.
For example, for a single layered Belt you might need 5mm thick strip whereas for adouble layer stitched belt get 2mm thickness and stitch them together.
You might want to use 1mm leather for extra soft feel for wallet, but 2mm for both inside and outside for extra heavy duty strengh.
EXOTIC ANIMAL HIDE
There are many different animal hide available, however cow is the most commonly available at good price and works great for All leather crafting. I recommend stick to cow hide to start, then as you develop skills and knowledge explore more exotic options.