Whenever dying anything leather, especially for the first time, test out on some scrap.
Nine times out of ten the dying process is more affected by the tanning process behind the leather, so sometimes you just ain't gonna win.
When using most leathers, I'll try and load up on Neatsfoot oil before dying. On some cowhides you can load up the oil alone, leave it out in the summer sun and end up with an attractive honey color. The oil will help spread the dye on any leather UNLESS you have a commercially tanned chromium base built into the tanning.
If it's off the shelf retail, the chances are that there is some chrome in there.
A lot of times a careful eye at Rendezvous will help you out before you even start your project. That pile of
Grey elk and Deerskin splits will accept a lot of different coloring schemes, and that uneven piece of cow can be fashioned into a piece with a lot of character if you have an eye for that . That's because they are separated from the retail skin and discarded before making it to market and the guy at rendezvous picked up a truckload before it was thrown out.
The basic rule of thumb for this stuff is this; If it's running around the woods and you shot it while carrying your tag, it'll be stretchy, pliable and soft. It'll really suck up color and will do so unevenly. If it put milk in your Cheerios, than the commercial processes will yield something you need to test out as a scrap because the various nationalities behind the products don't always perform well and the leather is not always well curried. Retail products don't always help you out.
Bags and accoutrements can be made from both, and you have a lot of good advice in these posts. This is a..."Touchy-Feely"...thing and the more you play around the better off your work will become over time.
Lastly, try to avoid rushing into your project. That's how you end up with end products that vary from your initial vision. Trust me...While converting from shoemaking to assembling rifle components, my impatience did that more than once, so the work trend is universal and not limited to your leather craft.
Hope this helps,
The Capgun Kid, AKA The Still River Cordwainer.