The guild bank is for everyone. Don't be discouraged to take items that will be of use to you. Removal of items just to sell on the Auction House is not permitted and will be met with Administrative Action.
Donations to the guild bank are encouraged, from extra items you don't need/want to spare gold (don't feel that you have to contribute 100g at a time, 1-2g at a time adds up quick, even a few silver).
(*Note: There are restrictions on the amount you can withdraw associated to your guild rank in-game.)
The latest Guild Bank Information can be be found here.