A bot that automatically buys and sells items would be against the rules but you can have a bot that gives suggestions on what items to buy. From what I remember anyway.
[23:23:53] <AndChat|700625> Blue eyes ultimate dragon best card
[23:24:29] <AndChat|700625> You know the one with 3 heads
[23:24:39] <~Lightningkid> just like my dick
[11:35:40] <box> Hampa suck
[11:36:21] <hampa> not the first to tell me that today
I already have a bot that can suggest price,eventually buy and even sell. Also sends PushNotifications to the phone but they're illegal... If staff allows me i can release the bot with just the suggest price and notifications functions.