Always use the fee if you send it for no fee your payment can take ages to arrive in the wallet
Thanks for your replies Entz & Newaw.
If I'm accepting 100s of transactions for only 1000 satoshi's, the fee will surpass the whole transaction... correct?
I've read about some gambling sites using their own blockchain or "off-blockchain mode" as they like to call it - what's this mean and how can I achieve it?
I think this is why a lot of sites have minimum withdrawl amounts that guarantee enough to cover a nominal fee. You could consider trying to send a very small fee (but I don't know if it would be ignored as dust, there's something about the settings of particular miners which is going to affect the order/number of transactions they try to load into a block), or setting a higher minimum withdrawl on your website.