The Epic Arena Shop is unique in that you earn tokens passively.
Guild Shop tokens will generally feel as scarce as Arena tokens. They're a good incentive to keeping Guilds full and active. More Guild members equal more GP, which equals more Raids, which equals more tokens for everyone.
Crucible Shop tokens are the easiest to obtain of all tokens. While it's recommended that you focus at most two Heroes in all other shops, you can spread out your purchases much more freely here. Again, DO NOT focus a single Hero to 7 stars.
The Arena Shop is probably the most important shop in which to manage your purchases carefully. Even placing relatively high for the daily reset regularly, you won't find you have a surplus of Arena tokens.