to buy Mobi you will need some Lumens on your balance.
buy XLM (or STR on poloniex) and send them to your wallet, it will automatically create your account as well.
Now after that you will have to set trust to MOBI issuer and buy as much as you want (but you'll need to leave 31 XLM on your balance to keep wallet active)
And I totally liked Stellar Disintegrated Network, I'm gonna call it that now. P.S. It's was Stellar Decentralized Exchange