I have a couple of different bags that I use depending on what I'm doing:
For general use , weapon storage, range carry and for when I have my stick in the truck vault of my work vehicle I use the eagle 29 inch SBR covert carry bag. Natchez had a crazy cheap deal on these and I think I bought 4 to augment the two I was issued. Price was like 50-70. It has two compartments and is very padded and durable.
For more covert carry (PSD, surveillance or if I otherwise need to be out in public with a hidden rifle) I use either the Noveske covert bag that first spear sells or the 2 vets arms backpack that LBT carries (carried). These work great for 10 inch SBRs and don't attract a ton of attention.
Lastly, for super compact long guns ( MP5 with stock collapsed or a 10 inch SBR with law folding stock) I have a sneaky bag covert carry bag (23 inch version). It looks like a regular back pack and no one gives me a second glance when I carry it around (it's light gray with black trim). I've also used this one countless times when I needed to have a hidden long gun while in public.
Best bag advice I can give you is to buy quality. All the bags I mentioned cost top dollar (@ $200) ( eagle bags were normally 100--150 when not on sale). Other advice is to determine what you want to use the bag for. In some cases, one stick will need 2 different bags to accommodate what you want to do.